Exploratory Study of Sustainability Practices in Worldwide Major Aircraft Maintenance,Repair,and Overhaul Companies

Abstract

While sustainable aviation research has primarily focused on the airline industry, aircraft manufacturing, and airport responsibilities, the aircraft maintenance, repair, and overhaul (MRO) industry’s contribution to achieving sustainable aviation goals has been overlooked. This study examines the approaches to corporate sustainability practices used by aircraft MRO companies worldwide. The methodology used to investigate the sustainability actions of major MRO companies globally was mainly based on observational data gathered from multiple data sources, such as environmental, social, and governance (ESG) and investor relations documents. Four companies out of the 13 major MRO companies whose sustainability reports were found are examined as a case study analysis. Each MRO company adopted different definitions and practices of sustainability. The findings show that the aircraft MRO sustainability definition varies among the major companies studied, but some commonalities can be used to develop a proposed definition. The authors propose that aircraft MRO sustainability be defined as the ability to conduct MRO business that positively affects all stakeholders while emphasizing safety, quality, and integrity values, using technology and innovation to make growth, and constantly stabilizing and/or diminishing the impact on the environment. This study contributes to the understanding of sustainable aviation by highlighting the role of MRO companies in achieving sustainable goals.

Keywords

sustainable aviation corporate sustainability environmental social governance (ESG)maintenance repair and overhaul (MRO)policy analysis

Aviation has evolved into a trusted and dependable form of transportation for both people and goods. Increased air travel implies more flights, which may lead to higher greenhouse gas (GHG) emissions as well as a more significant impact on environmental, economic, and social aspects ( 1 ). The International Civil Aviation Organization (ICAO) has increased its concern for the sustainable growth of international aviation by adopting various solutions, including “aircraft technology improvements, operational improvements, sustainable aviation fuels, and market-based measures” ( 2 ). The aviation industries need to operate sustainably to reduce the industry’s detrimental impacts while increasing social benefits.

Aircraft maintenance, repair, and overhaul (MRO) companies are a vital part of the aviation business, primarily because of their significant role in ensuring continued airworthiness and upgrades to aircraft. Sustainable aviation research has focused mainly on the airline industry, aircraft manufacturing, and airport responsibilities, but has paid little attention to the area of aircraft maintenance. Aircraft maintenance operations contribute to achieving sustainable aviation goals, such as how to treat waste products, how to conduct more efficient engine test runs, and how to maintain and upgrade aircraft to have a longer life. Aircraft MRO companies rarely display a sustainability section on their web page compared with most airlines’ websites. Therefore, it is not easy to understand the definition of sustainable MRO and measure the sustainability efforts of MRO companies comprehensively by considering the environmental, social, and economic impacts.

Early on, a lack of defined reporting frameworks and standards were two of the biggest challenges with reporting sustainability ( 3 ). Currently, corporation performance is measured not only from financial aspects but also from sustainability performance, which some corporations report as environmental, social, and governance (ESG) performance. Unlike financial reports, reports related to sustainability are still a voluntary corporate responsibility practice; not all countries have regulations in place that mandate the disclosure of ESG reports as compulsory requirements ( 4 ). However, sustainability reports are likely to become compulsory in the future ( 4 ). There are publicly held airlines that include ESG information in their annual reports and identify risks related to ESG. Previous research on sustainability in aviation has focused on quantitative analysis of sustainability in air transportation, airlines’ corporate social responsibility (CSR) issues, and sustainability reporting practices in U.S. airlines ( 5 – 7 ). In this paper, an exploratory study provides an in-depth analysis of the approaches to sustainability practices in major worldwide aircraft MRO companies.

Literature Review

Sustainability in Aviation Industry

Traditionally, the term “sustainability” in the aviation industry concentrated on environmental issues such as GHG emissions and noise pollution ( 8 ). Over the years, the concern for aviation sustainability has evolved into a broader definition. Sustainable air transportation implies its continuous development, adding economic benefits while at the same time alleviating its adverse social and environmental costs ( 9 ). In addition to environmental concerns, the air transportation sector is at the front line of people’s lives and safety while it continues to serve global travelers and incorporates huge and varied groups of workers ( 10 ). Economic and social sustainability are extremely important to the sector. Sustainability extends beyond protecting the environment ( 11 ).

ICAO agreed to a long-term aspirational goal aiming for net-zero CO₂ emissions from international aviation by 2050 ( 12 ). ICAO has formulated an international aviation carbon offsetting program called CORSIA ( 13 ). During the pilot and first phase of the program, CORSIA participation is voluntary. In January 2024, 126 ICAO members decided to voluntarily take part in implementing the scheme.

The Air Transport Action Group (ATAG) is an independent, non-profit aviation organization focusing on sustainable development concerns. Through ATAG, aviation industry executives made a notable commitment, the Aviation Benefits Beyond Borders, concerning the aviation world’s future development that focuses on economic growth, social development, and environmental efficiency ( 14 ). Based on ATAG’s definition, sustainable development is “taking the three priorities of the economy, society and the environment and finding ways of balancing these to produce the results that will benefit most people” ( 15 ). ATAG set a long-term objective to achieving net-zero carbon emissions by 2050 ( 16 ).

The International Air Transport Association (IATA) is an association of worldwide airlines. IATA does not explicitly define aviation sustainability; however, IATA creates initiatives to enhance aviation’s environmental performance ( 17 ). IATA shares the same long-term goal as ATAG ( 18 ).

Sustainable Aircraft Maintenance

Aircraft maintenance activities may have environmental consequences, such as the results of processing waste and end-of-life parts. The life cycle assessment of aircraft indicates that the impact of the maintenance phase on the environment is substantial and cannot be disregarded, contributing 5%–10% GHG emissions per aircraft life ( 19 ). Based on an evaluation of the U.S. Environmental Protection Agency 310-R-97-01 Air Transportation Industry topic document, the environmental impact of aircraft maintenance is comparable with the manufacturing stage and needs to become an important concern ( 20 , 21 ). Parts replacement, maintenance operations, and waste management are the three most critical main activities that must be managed because of the significant environmental impact ( 21 ).

Sustainable maintenance aspect can be defined as a combination of proactive technical, financial, and managerial operations carried out during a technological facility’s lifecycle to fulfil its functions while simultaneously assuring the attainment of objectives and the capacity to provide economic, environmental, and social aspect for all stakeholders over the long term ( 22 ). Singh and Gupta identified 14 factors that support the achievement of a sustainable maintenance entity ( 23 ). Top management commitment, comprehensive planning and execution, and a continuous improvement maintenance process to minimize production lead-time and costs are the essential components in ensuring a maintenance company’s sustainability advantage ( 23 ). No MRO companies have expressed a definition of sustainable MRO or use a sustainability framework explicitly designed for aircraft MRO entities.

Corporation Sustainable Actions

Since the Brundtland Report provided a widely recognized concept of sustainable development, many industries have started to adopt measures related to sustainable development and include them in their company reports ( 24 ). However, several industrial sectors have not fully reported their sustainability actions. In the past, the growth in sustainability reporting in industries other than air transportation was likely driven by regulatory compliance needs and public attention ( 25 ).

In recent years, there has been a considerable growth in the number of corporations reporting on sustainability efforts, driven not only by regulatory requirements but also by a growing understanding in the finance sector of the power that sustainability concerns—commonly called ESG concerns—have on financial performance and company value ( 26 ). According to legitimacy theory, businesses must always strive to guarantee that they operate within the boundaries and standards of society ( 27 ). Companies may use sustainability practices disclosure approaches to indicate that they include community expectations in their actions as a legitimizing tool. Additionally, the most powerful stakeholder groups affecting a company’s sustainability reporting transparency are investors and employees, because shareholder expectations can only be met if stakeholders are satisfied to some level beyond profitability ( 28 ).

Sustainability Reporting Framework

Sustainability or ESG reporting is now broadly expected by stakeholders, and the corporations that do not currently report may fall behind global norms ( 29 ). While sustainability is now mentioned in the objectives of some profit and non-profit organizations, determining the extent to which an organization is sustainable or pursues sustainable development can be complicated. One of the first sustainability reporting concepts used, claimed by Elkington, is the triple bottom line (TBL) ( 30 ). TBL is a framework that considers three aspects of sustainability performance: social, environmental, and financial concerns ( 30 ).

As an independent organization, the Global Reporting Initiative (GRI) has developed a standard for sustainability reporting that corporations and governments can adopt to publish their sustainable activities related to the economic, environmental, and social impacts ( 31 ). GRI offers a comprehensive and detailed reporting framework that meets all three aspects of the TBL framework ( 32 ). GRI was founded to create a standardized mechanism to ensure companies have attention to environmental impacts in their activities, which was then expanded to social, economic, and governance concerns ( 33 ). GRI underlines the “significance of the corporation’s role in climate change, human rights, governance, and social well-being” ( 34 ).

Based on the KPMG Survey of Sustainability Reporting 2020, GRI is the most commonly used sustainability reporting standard, with users being about 66% of the 100 largest corporations in 41 countries and around 75% of the world’s 250 largest corporations by revenue ( 26 ). Larger corporations are reviewed by the public and special interest groups that are likely to mount intense criticism about environmental and social welfare impacts. As a result, the size of the company significantly and favorably affects the publication of an ESG GRI-based sustainability report ( 35 ). GRI established essential criteria for the publication of a sustainability report in accordance with the GRI Standards. GRI mentioned that accuracy, balance, clarity, comparability, completeness, sustainability context, timeliness, and verifiability are the eight reporting principles that determine appropriate report content and quality ( 36 ). GRI did not publish specific sector standard for the aircraft MRO industry but has sector standards for specific industries such as oil, gas, and coal, as well as agriculture, aquaculture, and fishing ( 36 ). In general, large companies in the world use the sector standard in GRI to adapt the sustainability practices to the issues that need to be addressed.

Objectives and Research Questions

The goal of this research is to conduct an exploratory qualitative analysis of the application of sustainable action projects in major worldwide MRO companies. Publicly available ESG or related reports published by the major MRO companies worldwide were examined. The research questions addressed in this study are:

What are the conceptions of aircraft MRO sustainability used by major worldwide MRO companies?

What sustainability aspects have been undertaken by the major worldwide MRO companies?

Methodology

The exploratory study purpose is “to examine a little-understood issue or phenomenon to develop preliminary ideas and move toward refined research questions by focusing on the ‘what’ question” ( 37 ). The study’s two research questions are addressed using an exploratory multiple-case methodology with a single unit of analysis ( 38 ). The case study technique focuses on researching a phenomenon in its actual environment inside a constrained system, making it suited for exploratory studies where little or no hypotheses are known ( 38 ).

According to Yin, the multiple-case study is important work “to consider multiple cases as one would consider multiple experiments” ( 38 ). It means that a multiple-case study is similar to the replications process in multiple experiments. In this research, replication is the major MRO companies in the world that have published sustainability reports, web pages, or both, while the MRO sustainability practices is a single unit of analysis. The researchers identified definitions of sustainability by using narrative terms and ideas mentioned in the companies’ sustainability or ESG report documents. The methodology used to investigate the condition of sustainability actions of major MRO globally was mostly based on observational data gathering from multiple data sources, such as the available corporation public release or investor relations document. In further depth, the following steps of the researchers’ study procedure are carried out:

Identify the major MRO companies in the world based on different criteria such as airframe person-hours, total person-hours, and total revenue from several sources.

Compile several major MRO companies’ lists into a single list.

Identify the sustainability or ESG report and the year of publication from the official MRO company’s website on the list.

Select only the major MRO companies with a sustainability or ESG report and web page. Review the documents to find the sustainability definition, check their initiatives, and identify how to measure the initiatives and their long-term targets related to sustainability issues.

Identify similar themes and words used in the documents to define sustainable actions. Based on the statements provided, harmonize and formulate a definition of aircraft MRO sustainability.

Identify the focus areas utilized in the documentation for sustainable initiatives, such as environmental, economic, and social responsibilities.

Group the similar themes of sustainability actions that MRO companies have reported.

Construct an affinity diagram for sustainability activities and priority areas.

Develop a cross-case sustainability practice conclusion and report.

Data Collection

In this study, the sustainability and ESG data studied were those of MRO companies included in the world’s major MRO companies list. There are several versions of major categories from various market research sources based on different criteria; thus, the researchers present several lists for comparison. The criteria include annual airframe maintenance person-hours, total annual maintenance person-hours, and annual revenue. Data collection was carried out from September 1 to October 15, 2022, by exploring related websites. Table 1 presents the major MRO companies lists. From the lists of the major MRO companies available, researchers compiled a single list to explore their sustainability actions based on their ESG or sustainability report.

Table 1.

Major Maintenance, Repair, and Overhaul Companies in the World from Various Sources

No.	Aviation Week ( 39 )	Market Research Report ( 40 )	Thomasnet.com® ( 41 )	Verified Market Research ( 42 )
1	ST Engineering	HAECO	ST Engineering	HAECO
2	HAECO	ST Engineering	HAECO	ST Engineering
3	MRO Holdings	Lufthansa Technik	Lufthansa Technik	Lufthansa Technik
4	Lufthansa Technik	AFI KLM E&M	AAR	AFI KLM E&M
5	AAR	AAR	ATS	AAR
6	AFI KLM E&M	SIAEC		SIAEC
7	Ameco Beijing	Delta TechOps		Delta TechOps
8	GAMECO	SR Technics
9	EGAT	Turkish Technic
10	ATS	MRO Holdings

Of the 13 major MRO companies, sustainability reports were found for only four companies. Two MRO companies, AFI KLM E&M and Lufthansa Technik, each associated with airline companies, combined their sustainability reports with their parent companies’ reports. Therefore, determining the MRO company’s part of the company’s group report is complicated. Table 2 shows a summary of MRO companies where the researchers found a sustainability report.

Table 2.

Summary of Compiled Maintenance, Repair, and Overhaul (MRO) Companies List with Standalone Sustainability Report Available

MRO company name	Sustainability report	Year	URL source
ST Engineering	Sustainability Report 2021	2021	https://www.stengg.com/en/sustainability/sustainability-reports/sr2021/
HAECO	2021 Sustainable Development Report	2021	https://sd.haeco.com/media/t04kk2t1/haeco-group-sd-report-2021_en_compressed.pdf
MRO Holdings	Not found	NA	NA
Lufthansa Technik	Incorporated in Lufthansa Group Sustainability report	NA	NA
AAR	2021 Environmental, Social and Governance Report	2021	https://www.aarcorp.com/about/environmental-social-governance-esg/
AFI KLM E&M	Incorporated in AFI KLM Group Sustainability report	NA	NA
SIAEC	Sustainability Report 2021	2021	https://www.siaec.com.sg/pdf/SIAEC_SR_FY2020-21.pdf
Delta TechOps	Incorporated in Delta Air Lines, Inc. report	NA	NA
Ameco Beijing	Incorporated in Air China Ltd	NA	NA
GAMECO	Not found	NA	NA
EGAT	Not found	NA	NA
ATS	Not found	NA	NA
Turkish Technic	Not found	NA	NA

Note: NA = not available.

The four companies we found that have publicly available sustainability-specific reports are ST Engineering, HAECO, AAR, and SIAEC. A sustainability report was released once a year alongside the company’s annual financial report. Each company has a different format for reporting its initiatives into documents, so it is necessary to undertake a more extensive examination of descriptive terms to validate the actions made.

Results

This section presents a summary of data collected from the four MRO company sustainability reports or web pages which refer to the definition of sustainability, target priority areas, and current initiatives. This study follows the steps in the Methodology section, which was created using the multiple-case study replication logic technique to present individual case studies ( 38 ). The definition of sustainability in each company is identified by searching for keywords such as “sustainable development,”“vision,”“sustainability goal,”“ESG focus areas,”“sustainability,” and “CEO message” on the main page of the sustainability report or web page. After that, the target areas of each company and current sustainability practices are summarized from the published sustainability report.

Definition of Aircraft MRO Sustainability

The researchers studied the four MRO companies’ publicly available documents and found the definition of sustainability contained in their sustainability report or ESG report. Although none of them specified the definition of sustainability explicitly, the researchers identified definitions of sustainability by using narrative terms and ideas mentioned in the companies’ sustainability or ESG report documents to construe the definition of sustainability. Table 3 shows the statements related to the sustainability concept of each company used in the ESG or sustainability report.

Table 3.

Definition of “Sustainability” in Maintenance, Repair, and Overhaul Companies’ Sustainability Report Documents

ST Engineering

“To remain steadfast in positively impacting people’s lives and the health of our planet by operating responsibly in our communities and the wider global ecosystem. To create value by addressing real-world problems, including those related to climate change, urbanization and pandemics” ( 43 ).

HAECO

“Sustainable Development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs” ( 44 ).

AAR

“We constantly search for the right thing to do for our customers, our employees, our partners, and society. This guides our approach to further integrating ESG principles into our business and culture. We have a long history of prioritizing ESG values, such as quality and safety, inclusion, creative thinking, and integrity” ( 45 ).

SIAEC

“We create growth through innovation, technology and transformation, and collaborate with our business partners. We act responsibly, ensuring environmental and social sustainability in our operations and supply chain, with emphasis on the safety of our workforce and quality of our services. We contribute to our society and deliver value to our employees and local communities” ( 46 ).

Before this study, there was no literature found describing clearly what comprises aircraft MRO sustainability. The authors used the meaning and approach of sustainability after reviewing the available documents on sustainability from four MRO company cases to develop a general definition of sustainability in aircraft MRO companies. The new definition of aircraft MRO sustainability among worldwide MRO companies presented in this section answered Research Question 1.

Although the explicit definition of sustainability is not stated, ST Engineering has a vision of a sustainability approach with an emphasis on having an impact on human life and the environment, in the Group President and CEO statement. The statement implicitly reflects TBL’s elements: people, planet, and profit.

HAECO does not define sustainability their own definition, but they adopt the definition of sustainable development in the Brundtland Report (24). Sustainable development is defined as “development that meets the needs of the present, without compromising the ability of future generations to meet their own needs” ( 24 ). This broad idea does not explain precisely more in the context of HAECO’s MRO operations; consequently, the researchers must investigate further what action items they accomplished in the sustainability focus areas of the last sustainability report.

AAR takes a different approach in adopting the definition of sustainability. The researchers used descriptive words on the main page of the AAR website related to ESG and sustainability. The sustainability values emphasized in the AAR approach are “quality and safety, inclusion, creative thinking, and integrity” ( 45 ). In addition, AAR also stated that “the intended impact is on customers, employees, and society” ( 45 ).

SIAEC writes clearly its sustainable vision and action items overview in its sustainability report. In particular, they mentioned three main things in their sustainability framework: “creating change, responsible change, and delivering change” ( 46 ). Furthermore, SIAEC includes its main business aspects as the basis in its sustainability statement by mentioning, “We create growth through innovation, technology, and transformation, and collaborate with our business partners” ( 46 ).

Sustainability Targets and Initiative Areas

Sustainability practices are intended to accomplish goals in certain areas of each MRO company’s primary business and operations. Each company has a different structure and format in the sustainability report. A GRI index is included at the end of each report to refer to the pages they mention about the material topic. The researchers recognize descriptive words to define each of the four MRO companies’ sustainability program areas. The focus areas present a generalized group of sustainability goals that match with some standard sectors in the GRI framework. Tables 4 to 6 show, respectively, a list of sustainability targets, initiatives, and the latest conditions for actions that four MRO companies have taken.

Table 4.

Compiled Sustainability Targets by The Four Major Maintenance, Repair, and Overhaul Companies

Topic	ST Engineering	HAECO	AAR	SIAEC
Emissions	• 86,537,000 kg CO₂e by 2030 ( 43 , 47 )	• 63,993,380 kg CO₂e by 2030 ( 48 )	Not mentioned	• 24,370 CO₂e/$ million revenue by 2030/31 ( 49 , 50 ).
Energy	Not mentioned	Not mentioned	• Minimize energy use at key locations ( 51 ).	• Electrical consumption: 18,525,000 kWh by 2021/22 ( 46 , 49 ).
Water conservation	• The water usage target by 2025 is 618,800 m³ ( 43 , 52 ).	• Water intensity target by 2030 is 13.83 L/attended hour ( 48 ).	Not mentioned	Not mentioned
Waste management	Not mentioned	• Divert 60% of waste from landfill by 2030 ( 48 ).	• Our goal is to remove, repair and reuse or resell as much of a teardown as possible. If we cannot reuse or resell to our global customer base, then material may be recycled or sent for proper disposal. We also sometimes donate parts and materials to be used as furniture, art, or for educational materials ( 51 ).	Not mentioned
Environmental compliance	• Commitment to ethical business conduct and regulatory compliance ( 43 ).	Not mentioned	Not mentioned	• No environmental fines or other non-monetary ( 46 ).
Supplier environmental assessment	• Implementing environmental screening for all new suppliers worldwide ( 43 ).	• 100% of high risk and key suppliers in compliance with ethical and environmental standard as per supplier code of conduct ( 48 ).	• Suppliers must meet the minimum applicable regulatory standards on environmental impact ( 51 ).	• All suppliers are screened based on social and environmental factors ( 46 ).
Economic performance	Not mentioned	Not mentioned	Not mentioned	Not mentioned
Anti-corruption	• Zero tolerance for fraud and corrupt practices ( 43 ).	Not mentioned	• Zero cases of corruption or bribery ( 51 ).	• Zero cases of corruption or bribery ( 46 ).
Diversity and inclusion	• ST Engineering embraces fair employment practices and complies with all national and local labor laws and regulations where operating ( 43 ).	• HAECO Group aims to increase the proportion of female strategic leaders by 30% by 2030 ( 48 ).	• Our strength is rooted in our commitment to diversity, equity, and inclusion ( 51 ).	• Continue to support diversity and equality of opportunity in the workplace and in the boardroom ( 46 ).
Non-discrimination	• Establishing a workplace free from discrimination ( 43 ).	Not mentioned	• No discrimination issues ( 51 )	• Zero discrimination issues ( 46 )
Safety	• Our target is to have zero fatalities in our operations. We work toward lowering our major injuries year-on-year ( 43 ).	• The injury target and lost day rate in 2030 are 0.99 and 38.73, respectively ( 48 ).	• Committing to meet or surpass regulatory criteria while committing to the greatest degree of safety performance ( 51 ).	• Zero fatalities ( 46 )
Training and development	• Our focus is on growing the capabilities of a future-ready workforce that is equipped with new economy skills and empowered for success ( 43 ).	Not mentioned	Not mentioned	• Maintain an annual average of 34 h of training per employee ( 46 ).
Community contribution	• Strengthen communities further through our three focus areas.• Encourage staff volunteerism ( 43 ).	• Increase by four times volunteering hours per employee by 2030 versus 2018 baseline (4,000 h/14,700 employee). Therefore, the target by 2030 is 1 volunteering hour per employee.• Establish corporate social responsibility foundation fund min. 1% of annual profits ( 48 ).	• Support nonprofits and organizations that work to improve society, with an emphasis on veterans’ programs and education for high school and college students ( 51 ).	Not mentioned
Human rights	Not mentioned	Not mentioned	• Zero-tolerance stance for human trafficking and forced labor ( 51 ).	Not mentioned

Note: CO₂e = carbon dioxide equivalent; kg = kilogram(s); L = liter(s); kWH = kilowatt hour(s); h = hour(s).

Table 5.

Compiled Sustainability Initiatives by The Four Major Maintenance, Repair, and Overhaul Companies

Topic	ST	HAECO	AAR	SIAEC
Emissions	• Reducing Scope 1 emissions by optimizing operational activities such as delivery runs, engine test cell usage and vehicle testing.• Reducing Scope 2 emissions by installing solar PV systems across global sites.• Reducing Scope 3 emissions by reducing air travel and conducting virtual meetings where possible ( 43 ).	• Installed 3 MW solar photovoltaic (PV) systems.• Explored the usage of sustainable aviation fuel, with the goal of incorporating 10%–15% use into their overall consumption by 2030.• Scope 3 emission reduction project was started to understand carbon footprint ( 48 ).	• Reduced electricity consumption and increasing the use of renewable energy from utility providers in an effort to reduce Scope 2 emissions ( 51 ).	• Installed solar PV systems on five hangars and engine test facility.• Conducted a feasibility study to replace petrol-based vehicles with electric vehicles.• Began a test of electric tow tractors, which produce 55% fewer carbon emissions than traditional tractors ( 46 ).
Energy	Not mentioned	Not mentioned	• Reduced electricity utilization by 40,000 kWh in 2017 and 2018 in Amsterdam facility.• Installed LED lighting in Michigan, New York, Miami, and Oklahoma facilities.• Upgraded to LED lighting in Illinois facility.• Improved tracking and data collection of utility energy ( 51 ).	• Established a control system for energy management that tracks energy use.• Installed motion detectors and replacement of the illumination with LEDs.• Utilized an effective central chilled water system for air conditioning in buildings.• Setup of pumps with variable-speed drives ( 46 ).
Water conservation	• Install smart water meters at more locations to enhance tracking.• Install water-saving devices such as water thimbles and flow-reducing valves.• Promote water conservation awareness through toolbox briefings and campaigns.• Perform regular checks to detect leakages in pipes and faucets ( 43 ).	• Built wastewater treatment facility to reuse the water which is able to process 150 tonnes of wastewater per day.• Developing robotic aircraft dry washing process to further reduce water usage ( 48 ).	• Installed a chiller at one of its facilities that recirculates chilled water to cool presses as opposed to using city water from a well field that was released to the sewer ( 51 ).• Recycled water is used to wash the aircraft ( 51 ).	• Monitors the data on water use and performs monthly inspections of water pipelines and valves to make sure there are no leaks.• Maintain effective water treatment systems for cooling towers.• Collect rainwater at three hangars which is utilized to fill cooling towers with water and flush bathrooms.• Obtain Water Efficient Building Certification from the Public Utilities Board.• Managing water as a common resource ( 46 ).
Waste management	• Use fewer materials and consumables, reduces the reliance on paper, recycles existing materials such as wooden pallets, and recycle used oil, manufacturing materials, paper, and e-waste ( 43 ).	• Fully adopt the waste-to-energy initiative in all Xiamen facilities.• Divert more than 98% of waste from landfills.• Increasing food waste recycling volume by 57% compared with the prior month ( 48 ).	• Repair, rebuild, and refurbish all aspects of an aircraft as needed ( 51 ).• Obtain as much value as possible from the components ( 51 ).	• Publish instructions on how to dispose of dangerous industrial waste properly.• Introduced trash sorting and disposal methods, as well as a contamination preventive procedure supervised by a licensed toxic industrial waste collector.• Waste reduction in offices and operational operations.• Campaign 3R (reduce, reuse, recycle) ( 46 ).
Environmental compliance	• Risk and compliance training has been expanded to encompass more regulatory compliance subjects. Stakeholders have been enlisted to help enhance the business risk management process ( 43 ).	Not mentioned	Not mentioned	• Ensure adherence to all governing guidelines and pertinent environmental standards that apply to operations and services ( 46 ).
Supplier environmental assessment	• Environmental concerns have been added as a new supplier screening criterion in Singapore operation ( 43 ).	• The procurement selection process was further enhanced by defining more sustainable development evaluation criteria to minimize the impact to the environment. Recognizing the benefits of plastic material usage control, a sourcing policy for plastic items was also established ( 48 ).	• The AAR Supplier Code of Conduct applies to all third parties engaged in business dealings with AAR to meet the Environmental Impact Standard ( 51 ).	• Suppliers must provide applicable sustainability track records, certificates, or standards (ISO 14001, ISO 9001, ISO 45001, BizSafe Certification, and so on) in their submissions ( 46 ).
Economic performance	Not mentioned	Not mentioned	Not mentioned	• SIAEC generates S$443 million in revenue and distributes S$247.5 million in operating costs, employee salaries and benefits, interest payment, and taxes ( 46 ).
Anti-corruption	Not mentioned	Not mentioned	• Annual anti-corruption training for new recruits and workers.• Do not offer, give, or accept, directly or indirectly, any bribes, kickbacks or other corrupt payments, regardless of whether working with commercial entities or government officials, including employees at state-owned or -controlled airlines ( 51 ).	• Establish a whistleblower program, an employee code of conduct, a supplier code of conduct, and an anti-corruption/anti-bribery policy ( 46 ).
Diversity and inclusion	• We commit to fair employment practices and offer merit-based equal opportunities to all, including promoting training and skills development. We do not discriminate according to age, race, nationality, religion, gender or marital status ( 43 ).	• HAECO held an Ethnicity Day to spread the message through mini games and international cuisines.• The Women’s Network and Male Allies organized a wide range of activities with more than 1,000 participations• HAECO celebrates Pink Friday, to support LGBT+ inclusion ( 48 ).	• Promote diversity hiring ( 51 ).• A women-focused Employee Resource Group (ERG) was founded in 2015, with the goal of advancing the careers of women at AAR ( 51 ).• In 2021, AAR established VRG, a veteran-focused ERG for workers from the military background ( 51 ).	• The ideals of inclusion and equal opportunity serve as the foundation for people management policies and procedures.• Collaborate with Women in Aviation International, a non-profit organization dedicated to the encouragement and advancement of women in all aviation career fields and interests, to invite women to have a career in this industry ( 46 ).
Non-discrimination	• HR Policy provides a process to manage grievances because of discrimination ( 43 ).	Not mentioned	• AAR does not base hiring choices on a person’s constitutionally protected personal traits ( 51 ).	• Avoid discriminatory behavior, including but not limited to that based on age, gender, religion, nationality, and handicap ( 46 ).
Safety	• Adopting ISO 45001 Occupational Health and Safety Management Systems revising our WSH indicators, carrying out a group-wide WSH promotion and campaign, enhancing WSH digital platforms (e.g., injury reporting, hazard reporting) and emphasizing mental wellbeing at our workplaces ( 43 ).	• Establishment of Group Safety and Quality Management Framework• Develop HAECO Integrated Standards and Recommended Practices• Improve near-miss reporting for proactive risk management ( 48 ).	• Implementing SMS program.• Proactively eliminating hazards and contain or mitigate risks.• Utilizing consumer input to enhance the quality of our procedures ( 51 ).	• Implement Promotion Centre, Safety and Security Week, and Maintenance Line Operations Safety Assessment Program” ( 46 ).• Implement safety management system ( 46 ).• Conduct occupational health and safety training and communication ( 46 ).• Collaborate with stakeholders in promoting safety ( 46 ).
Training and development	• Carry out learning needs analysis and develop an annual training plan (including on-the-job training).• Offer a global leaders development program to develop globally oriented management via postings to our business units across geographies.• Provide flexible career tracks where employees can move between management or technical tracks to gain exposure.• Create a pool of potential successors for key positions through our talent management programs ( 43 ).	Not mentioned	• AAR held management training classes focused on soft skills development, management training, leadership development, and career development ( 51 ).	• The company offers organized training and development programs that help employees develop both technical and soft abilities ( 46 ).
Community contribution	• Improving lives through charitable gifts, enriching lives through education, and touching lives through engineering ( 43 ).	• Promoting environmental and social initiatives through corporate social responsibility (CSR) program.• Donating funds to more than 20 NGOs that focus on youth, elderly, and minority society ( 48 ).	• Help NGOs and organizations that work to better society ( 51 ).	• Through collaborations with Food from the Heart, Community Chest, and Habitat for Humanity, CSR initiatives aim to provide housing and food assistance to communities in Singapore and Southeast Asia ( 46 ).
Human rights	Not mentioned	Not mentioned	• All employees are trained annually on the principles of Supporting Human Rights: Modern Slavery Act ( 51 ).	Not mentioned

Note: MW = megawatt(s); PV = photovoltaic; kWH = kilowatt hour(s); LED = light emitting diode; LGBT+= lesbian, gay, bisexual, transgender, and other sexual identities; NGOs = non-government organisations; WSH = workplace safety and health; SMS = safety management system; CSR: corporate social responsibility.

Table 6.

Compiled Recent Sustainability Condition by the Four Major Maintenance, Repair, and Overhaul Companies

Topic	ST	HAECO	AAR	SIAEC
Emissions	• 120,900,000 kg CO₂e absolute greenhouse gas (GHG) emissions. 30% reduction in GHG emissions compared with 2010 levels ( 43 ).	• 9.4% Carbon emission reduction compared with 2020 level, 61,513 tonnes CO₂e (scope 1 and 2) ( 48 ). Target was achieved in 2021, 43% lower than 2018 baseline.	• Scope 1 emissions: 25,151,000 kg CO₂e and • Scope 2 emissions decreased by 23.4% to 19,069,000 kg CO₂e ( 51 ).	• The total intensity CO₂e emissions in financial year (FY) 2020/21 was 30,000 kg CO₂e/$ million revenue, greater 1% than FY 2013/14 ( 46 ).
Energy	Not mentioned	Not mentioned	• Energy use decreased by 5.5% compared with previous year. Energy use in 2021 was 184,330 MWh ( 51 ).	• The total energy consumption was 145 TJ, 28% less than in FY 2013/14 ( 46 ). The reduction was mainly attributed to reduced business activities caused by COVID-19 ( 46 ).
Water conservation	• Water consumption in 2021 was 638,000 m³. “In 2021, water consumption intensity decreased by 15% compared with the intensity in our 2015 base year ( 43 ). The target was achieved in 2021.	• Water intensity 14.47 L /attended hour ( 48 )	Not mentioned	• The total amount of water removed fell from 97,900 m³ in FY 2019/20 to 71,866 m³ in FY 2020/21, a 27% decline ( 46 ).
Waste management	• Recycled 78% of 5,900 tonnes of waste generated ( 43 ).	• 53.4% waste diversion from landfill in 2021, an increase of 40.1% from the previous year ( 48 ).	• Of the approximately 1.6 million parts available in the PAARTS store, approximately 59% are used serviceable material (USM) parts ( 51 ).	• SIAEC generated a total of 2,156 tonnes of waste, of which 67 tonnes of non-hazardous waste was diverted through recycling efforts. The remaining 2,089 tonnes of waste, comprising 538 tonnes of non-hazardous waste and 1,551 tonnes of hazardous waste, was disposed according to regulatory requirements ( 46 ).
Environmental compliance	• No significant fines or non-monetary sanctions for non-compliance with environmental, health, and safety regulations ( 43 ).	Not mentioned	Not mentioned	• Zero environmental or non-monetary penalties ( 46 ).
Supplier environmental assessment	• ST Engineering Vendor Code of Conduct recognized by strategic suppliers in Singapore operations ( 43 ).	• 78% of high-risk and key suppliers in compliance with ethical and environmental standard as per supplier code of conduct ( 48 ).	Not mentioned	• Suppliers provide applicable sustainability track records, certificates, or standards (ISO 14001, ISO 9001, ISO 45001, BizSafe Certification, and so on) in their submissions ( 46 ).
Economic performance	Not mentioned	Not mentioned	Not mentioned	• SIAEC generate S$443 million in revenue and distribute S$247.5 million in operating cost, employee salary and benefit, interest payment and taxes ( 46 ).
Anti-corruption	• Zero tolerance for fraud and corrupt practices ( 43 ).	Not mentioned	• No corruption or bribery cases ( 51 ).	• No corruption or bribery cases ( 46 ).
Diversity and inclusion	• Age group (in years): 15% <30, 26% 30–40, 27% 40–50, 23% 50–60, 9% 60+• By geography: 63% Singapore, 23% North America, 10% Europe, 4% other• 79% male and 21% female employees• 85% male and 15% female supervised workers• 15% of male and 14% of female employees are people managers ( 43 ).	• 87% male and 13% female strategic leaders ( 48 )	• Age group: 16% <30, 20% 30–40, 22% 40–50, 26% 50–60, 16% 60+• 72% male and 18% female employees• 49% minority• 22% veteran ( 51 ).	• 89% male and 11% female employees;• 99.4% male and 0.6% female fixed-term-contract employees• 77.4% male and 22.6% female managers• Manager age group: 73% 30–50 and 27% 50+• 76.4% male and 23.6% female executives• Executive age group: 21.8% <30, 60.1% 30–50, 18.1% 50+• BOD breakdown: 90% male and 10% female• BOD age group: 10% 30–50, 90% 50+• 88% male and 12% female total new hires ( 46 )
Non-discrimination	• Two cases of discrimination in 2021 ( 43 )	Not mentioned	• No discrimination reported cases ( 51 )	• No discrimination reported cases ( 46 )
Safety	• The accident frequency rate and accident severity rate in 2021 were 1.1 and 22.0, respectively ( 43 ).	• 3.00 total injury rate• 62.49 lost day rate ( 48 )	Not mentioned	• Zero fatalities• Employee work-related injury rate: 4.72• Third-party worker work-related injury rate: 2.66• Employee recordable work-related injury rate: 4.25• Third-party worker recordable work-related injury rate: 2.66 ( 46 ).
Training and development	Not mentioned	Not mentioned	• Provides all employees with learning opportunities through on-the-job training, quarterly “lunch and learn” events, tuition reimbursement (up to $10,000 a year) and priority application opportunities for all open jobs ( 51 )	• In 2020/21, employees received an average of 50 h of training ( 46 ).
Community contribution	• $2.8 million donations and sponsorship to the communities ( 43 )	• HKD$3 million charity donation and around 1,000 volunteering hours ( 48 )	Not mentioned	• Access to food: S$50,000 donated to annual charity run, S$66,000 donated to Food from the Heart organization and S$5,000 donated to Community Chest ( 46 ).• A decent place to live: employee volunteers participate in the HomeWorks project organized by the Habitat for Humanity program by working with families in need to help clean their homes ( 46 ).
Human rights	Not mentioned	Not mentioned	Not mentioned	Not mentioned

Note: CO₂e = carbon dioxide equivalent; kg = kilogram(s); L = liter(s); MWH =megawatt hour(s); TJ = terajoule; BOD = board of directors.

In their MRO sustainability reports, each of the four MRO companies developed their sustainable focus categories that represent their interests based on the specific needs and elements essential to the company and their external impact. By analyzing the categories of sustainability action and the targets they want to achieve related to MRO operations and other relevant content, the researchers identified the thematic areas of sustainable initiatives and carried out the note-taking process for constructing an affinity diagram. The researchers then re-reviewed the documents to double-check the information retrieved from these and ensure this is displayed correctly in individual case studies. An affinity diagram was developed based on the key terms and phrases of sustainability actions; the researcher combined and aligned them into several thematic areas and their associated subareas that cross the four cases, as shown in Table 7.

Table 7.

An Affinity Diagram of Sustainability Practices in Worldwide Major Aircraft Maintenance, Repair, and Overhaul Companies

Focus topic area	Specific subtopic project
Environmental
Emissions	• Renewable energy
	• Sustainable aviation fuel
	• Operational optimization
	• Electric vehicle
Energy	• LED bulbs installation
	• Energy monitoring systems
	• Energy load-based sensor (motion sensor, VSD)
Water conservation	• Water recycling
	• Water tracking
	• Regular leak inspection
	• Rainwater collection
Waste management	• 3R (reduce, reuse, recycle) encouragement
	• Fewer materials and consumables
	• Reduce landfill waste
	• Waste reduction campaign
Environmental compliance	• Risk and compliance training
Environmental compliance	• Create guidelines and standard
Supplier environmental assessment	• Add environmental concern supplier screening criteria
Economics
Economic performance	• Total revenue
Governance
Anti-corruption	• Employee anti-corruption training
	• Develop an anti-corruption code of conduct and policy
	• Whistleblower program
Social
Diversity and inclusion	• Fair employment and merit-based people management policy
	• Diversity hiring program
	• Support LGBT+ inclusion
	• Create a women-focused employee resource group
Non-discrimination	• Create non-discrimination-policy
Safety	• Establishment of group safety and quality management framework
	• Conduct occupational health and safety training and promotion
	• Establish near-miss reporting for proactive risk management
	• Implement safety management system
Training and development	• Employee soft-skills training
	• Flexible career track program
	• Create a talent pool management program
Community contribution	• Fund donation to NGO
	• Provide food and housing to communities
	• Promote environmental and social initiatives
Human rights	• Supporting human rights: Modern Slavery Act knowledge training

Note: VSD = variable speed drive; LED = light emitting diode; LGBT+ = lesbian, gay, bisexual, transgender, and othe sexual identities; NGO = non-government organisation.

The environmental theme is a significant concern for MRO companies in sustainability issues. The four companies’ most adopted sustainability goal and the action focus area are: emissions, water conservation, and waste management issues. Reducing GHG emissions to certain levels and different target years for each company has become one of the main issues widely discussed in the four MRO companies’ sustainability reports. The implementation of renewable energy, such as installing solar photovoltaic systems, is one widely adopted action taken by the four companies to reduce the emission figures. Water conservation is also one of the aspects that the four companies have undertaken in pursuing sustainability business. However, only ST Engineering and HAECO specifically mention targets they want to achieve and the time target. The four MRO companies are concerned about waste management while “reduce, reuse and recycle” (3R) is the popular framework they use to minimize the amount of disposal waste. In this case, only HAECO has the exact figure to achieve.

The four companies also have concerns about the environmental impacts caused by their supply chain process. The companies may be involved in adverse environmental consequences because of business partnerships with suppliers or other parties. All companies have a standard screening process for their suppliers to comply with environmental impact standards. For example, suppliers must provide a sustainability track record to get accepted.

The companies also focus on social themes to maintain a sustainable business. Diversity and inclusion are principles they hold to support their employees, either in the recruitment process or while already working in the company. MRO companies have similar concerns about women’s involvement in aviation by supporting women-focused resource groups. Furthermore, the age demographic and the proportion of men and women are shown in the sustainability reports of the four companies. Moreover, aligned with diversity and inclusion concerns, all companies have a goal of zero discrimination issues.

Safety is a social core value in the aviation business and is mentioned by the four MRO companies in their sustainability documents. The MRO companies want to minimize the number of fatalities as a target. Initiatives taken by ST Engineering, such as adopting the ISO 45001 Occupational Health and Safety Management System, and the implementation of the SMS program by AAR and SIAEC, are examples of programs for minimizing work accidents. Other common social sustainability actions taken by MRO companies include training and development for their employees and community contributions through CSR programs. One company, AAR, touched on the issue of human rights—human trafficking and forced labor—in its sustainability initiative and target.

All MRO companies in this case study are concerned with implementing good governance with the specific goal of zero cases of corruption in their organizations. Establishing a whistleblower program and anti-corruption training are initiatives undertaken by AAR and SIAEC, respectively.

Discussion

The definition of aircraft MRO sustainability is varied, and the four companies exhibit differences in their perspectives. However, there is some commonality in their definitions. Based on the study conducted in this paper, the viewpoints are harmonized by the researchers. The researchers propose this definition of aircraft MRO sustainability:

Aircraft MRO sustainability is the ability to conduct MRO business that positively impacts all stakeholders—customers, employees, partners, and society—making growth through technology and innovation by emphasizing safety, quality, and integrity values while constantly stabilizing and/or diminishing the impact on the environment.

The phrase “positively impacting all stakeholders—customers, employees, partners, and society” represents the sustainable impact aim in ST Engineering and AAR ( 43 , 45 ). The statement “making growth” is paraphrased from the desire to grow in all selected MRO companies in this study, while the phrase “through technology and innovation” is taken from the SIAEC statement ( 46 ). The words “by emphasizing safety, quality, and integrity values” are included because these values are a widely recognized priority in maintaining aviation safety; these values are also explicitly stated in the AAR and SIAEC statements ( 45 , 46 ). The phrase “constantly stabilizing and/or diminishing the impact on the environment” represents efforts to reduce environmental impact, as mentioned by ST Engineering ( 43 ). However, it is essential to note that, while ST Engineering prioritizes this goal, the primary objectives of ICAO, ATAG, and IATA are in reducing GHG emissions. The researchers hold the viewpoint that aircraft MRO sustainability should be defined and that the definition should represent the priority purposes of aircraft MRO and associate with the other three aspects; economic, social, and environmental.

In performing sustainability projects, the four MRO companies took different approaches. The emphasis areas chosen by each MRO company gave an idea of what the MRO company deems priority areas. All four MRO companies have common initiatives to reduce GHG emissions. Reducing GHG emissions is a 2030 target for ST Engineering, HAECO, and SIAEC, while AAR does not mention specific targets for reducing emissions by 2030. This topic is in line with ICAO and ATAG’s concern about the aviation industry’s support to the achievement of the United Nations 2030 Agenda for Sustainable Development (UN SDG) ( 53 , 54 ). As far as target metric is concerned, units in ratio scale, such as CO₂e/$ million revenues set by SIAEC, clearly describe their environmental impact compared with the economic performance. This metric may be an appropriate reference for other MRO companies. However, the four MRO companies do not report an operational strategy for reducing emissions through performing more efficient aircraft engine run-up tests during the maintenance event. Aircraft engine operations are a significant contributor to GHG emissions in the aviation industry.

Energy-related actions are another common topic of focus in the environmental sustainability area adopted by MRO companies. Energy-related projects, such as installing motion sensors or installing LED lamps to reduce building power consumption, are easier to implement and have lower capital costs than other projects ( 11 ). Simultaneously, energy reduction projects are known to have a positive impact on reducing emissions.

As far as water conservation and waste management are concerned, ratio scales such as “L/attended hour” and “divert 60% waste from landfill,” as set by HAECO, may be implemented by all MRO companies. Uniformity of water conservation and waste management targets need to be established to measure sustainability performance. All selected MRO companies have projects to reduce water use and waste, although not all of them have targets. As an operational improvement effort for aircraft, engine water wash is a maintenance item to reduce engine exhaust emissions; on the other hand, it consumes considerable water ( 55 ). This study finds that no major MRO companies have a reported strategic project to perform aircraft engine wash tasks and aircraft cleaning more efficiently to reduce water consumption.

The research findings indicate that the sustainability reports lack clear representation of economic benefits for the community. Most of the selected MRO companies in the GRI index section refer to the annual financial report to see the economic performance. This economic or financial performance should be accommodated along with any initiatives that support long-term financial stability, which will create value for communities in future sustainability reports.

The social sustainability theme was widely adopted by the four companies and is a critical part of the MRO business, which is labor-intensive and has great potential effect on the surrounding community. From this study, the safety focus topic stood out in all companies. Safety is widely known to be a fundamental principle in air transportation. Therefore, all companies highlight safety issues concerning both targets and initiatives they undertake. Other social sustainability themes that focus on employee stakeholders are non-discrimination, diversity, and inclusion. The projects carried out by the four MRO companies, such as encouraging women and supporting diversity hires, align with the issue of inclusiveness in UN SDG No. 5: Gender Equality ( 56 ). MRO companies need to improve their progress toward the UN SDG No. 5 and consistently carry out this effort sustainably for years to come.

The findings of this study indicate that aircraft MRO companies are making an effort in community contributions through CSR activities. Of the four companies, only HAECO has specific goals in this focus by setting a target of 1 volunteering hour per employee by 2030 and establishing a CSR fund of at least 1% of annual profit. Quantitative targets for communities like this should be adopted by each MRO company to enhance measurability in assessing the provided impact.

The affinity diagram (Table 7) developed by the researchers explains what measures were taken by major worldwide MRO companies in achieving sustainability goals in 2021. This diagram can be an initial reference for starting sustainability initiatives with additional items such as economic sustainability performance. Moreover, in this study, it was found that, in all sustainability reports, only a few aspects of sustainability had quantitative target parameters. In contrast, most aspects were described without specific targets and were referred to as commitments. While targets and goals are inherently commitments, in this context, “commitments” refers to statements without quantifiable parameters. An MRO company management team should consider the benefits of setting metrics using quantitative data because this can be a baseline parameter that is easy to compare with future progress.

Conclusion

Aircraft MRO sustainability has become an essential part of the aviation industry to consider when aiming to achieve the common goal of sustainable aviation. MRO companies strive to provide airworthy, safe, high-quality service for the aircraft customer. To do so sustainably, they must do it economically without negatively affecting the environment and society. Currently, there is no specific research on sustainability for the aircraft MRO industry, while the airlines and airport industry have been widely researched. This research initiates the exploration of aircraft MRO sustainability by establishing an initial definition applicable to all MRO companies and relevant sustainability themes within the industry. This exploratory qualitative research employs a multiple-case study methodology to investigate definitions and topics of sustainability initiatives adopted by major worldwide aircraft MRO companies. An understanding of aircraft MRO sustainability was developed based on each company’s sustainability viewpoints in relation to MRO sustainability initiative categories, targets, planned actions, and related parameters.

The findings show that only 4 of 13 major worldwide MRO companies have published a specific sustainability or ESG report. No single sustainability or ESG framework was adopted in all reports. Each MRO company adopted multiple sustainability definitions and practices. A proposed definition of aircraft MRO sustainability was developed based on integrating the viewpoints of four major aircraft MRO companies. A set of sustainability initiative focus areas that the MRO companies have carried out is shown in an affinity diagram, and suggestions to improve are presented in the Discussion section.

The definition of aircraft MRO sustainability in this study is a foundation for future research and may encourage aircraft MRO companies to expand their sustainability views and initiatives. As discussed in this study, quantitative sustainability metrics should be used to measure sustainability performance and set targets. Future research on this topic may include by creating a sustainability concept that regulators and aircraft MRO companies can agree on, developing a set of quantitative sustainability targets to help MRO companies measure sustainability performance and develop technique to assess and select appropriate sustainability projects.

Footnotes

Author Contributions

The authors confirm contribution to the paper as follows: study conception and design: G. Swastanto, M. Johnson; data collection: G. Swastanto; analysis and interpretation of results: G. Swastanto; draft manuscript preparation: G. Swastanto, M. Johnson. All authors reviewed the results and approved the final version of the manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Gita Andhika Swastanto

Mary E. Johnson

References

Air Transport Action Group. Sustainability. https://www.atag.org/our-activities/sustainable-development.html. Accessed April 25, 2024.

ICAO. Climate Change. https://www.icao.int/environmental-protection/pages/climate-change.aspx. Accessed January 23, 2022.

Janić

Developing an Indicator System for Monitoring, Analyzing, and Assessing Airport Sustainability. European Journal of Transport and Infrastructure Research, Vol. 10, No. 3, 2010, pp. 206–229. https://doi.org/10.18757/EJTIR.2010.10.3.2889.

KPMG International. The KPMG Survey of Corporate Responsibility Reporting 2017. KPMG International, Zurich, Switzerland, 2017.

Janic

The Sustainability of Air Transportation. Routledge, Florence, 2017.

Rudari

Johnson

Sustainability Reporting Practices of Group III U.S. Air Carriers. International Journal of Aviation, Aeronautics, and Aerospace, Vol. 2, No. 2, 2015, p. 5. https://doi.org/10.15394/ijaaa.2015.1066.

Peeters

Bouwer

Bongaerts

Eijgelaar

Airlines and Corporate Responsibility: Issues and Challenges, In Corporate Sustainability and Responsibility in Tourism (D. Lund-Durlacher, V. Dinica, D. Reiser, and M. Fifka, eds.), Springer, Cham, 2019, pp. 163–180.

Upham

Towards Sustainable Aviation. Routledge, London, 2003.

Janić

Greening Airports: Advanced Technology and Operations. Green Energy and Technology, Vol. 52, 2011, p. 1. https://doi.org/10.1007/978-0-85729-658-0.

10.

Kemp

L. J.

Vinke

CSR Reporting: A Review of the Pakistani Aviation Industry. South Asian Journal of Global Business Research, Vol. 1, No. 2, 2012, pp. 276–292. https://doi.org/10.1108/20454451211252778.

11.

Prather

C. D.

Airport Sustainability Practices: Drivers and Outcomes for Small Commercial and General Aviation Airports. Transportation Research Board, Washington, D.C., 2016.

12.

ICAO. Long Term Global Aspirational Goal (LTAG) for International Aviation. https://www.icao.int/environmental-protection/Pages/LTAG.aspx. Accessed March 1, 2024.

13.

ICAO. Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). https://www.icao.int/environmental-protection/CORSIA/Pages/default.aspx. Accessed November 8, 2022.

14.

ATAG. Aviation: Benefits beyond Borders. Air Transport Action Group, Geneva, Switzerland, 2014.

15.

ATAG. Sustainability. https://www.atag.org/our-activities/sustainable-development.html. Accessed April 25, 2024.

16.

ATAG. Climate Action. https://www.atag.org/our-activities/climate-change.html. Accessed April 25, 2024.

17.

Johnson

M. E.

Exploring Assessment Metrics for Airport Operational Sustainability. Proc., International Annual Conference of the American Society for Engineering Management, Huntsville, 2017.

18.

IATA. IATA - Environment. https://www.iata.org/en/programs/environment/. Accessed November 9, 2022.

19.

Chester

M. V.

Life-Cycle Environmental Inventory of Passenger Transportation Modes in the United States. University of California, Berkeley, 2008.

20.

U.S. Environmental Protection Agency. EPA Office of Compliance Sector Notebook Project. Air Transportation Industry, EPA 310-R-97-001. U.S. Environmental Protection Agency, Washington, D.C., 1998.

21.

Keivanpour

Kadi

D. A.

A Sustainable Approach to Aircraft Engine Maintenance. IFAC-PapersOnLine, Vol. 48, No. 3, 2015, pp. 977–982. https://doi.org/10.1016/j.ifacol.2015.06.210.

22.

Jasiulewicz-Kaczmarek

Żywica

The Concept of Maintenance Sustainability Performance Assessment by Integrating Balanced Scorecard with Non-Additive Fuzzy Integral. Eksploatacja i Niezawodnosc - Maintenance and Reliability, Vol. 20, No. 4, 2018, pp. 650–661. https://doi.org/10.17531/ein.2018.4.16.

23.

Singh

R. K.

Gupta

Framework for Sustainable Maintenance System: ISM–Fuzzy MICMAC and TOPSIS Approach. Annals of Operations Research, Vol. 290, No. 1–2, 2020, pp. 643–676. https://doi.org/10.1007/s10479-019-03162-w.

24.

Brundtland Commission. Report of the World Commission on Environment and Development: Our Common Future. Oxford University Press, New York, 1987.

25.

Kolk

A Decade of Sustainability Reporting: Developments and Significance. International Journal of Environment and Sustainable Development, Vol. 3, No. 1, 2004, p. 51. https://doi.org/10.1504/IJESD.2004.004688.

26.

KPMG International. The Time Has Come: The KPMG Survey of Sustainability Reporting 2020. KPMG International, Zurich, Switzerland, 2020.

27.

Ching

H. Y.

Gerab

Sustainability Reports in Brazil through the Lens of Signaling, Legitimacy and Stakeholder Theories. Social Responsibility Journal, Vol. 13, No. 1, 2017, pp. 95–110. https://doi.org/10.1108/SRJ-10-2015-0147/FULL/PDF.

28.

Fernandez-Feijoo

Romero

Ruiz

Effect of Stakeholders’ Pressure on Transparency of Sustainability Reports within the GRI Framework. Journal of Business Ethics, Vol. 122, No. 1, 2014, pp. 53–63. https://doi.org/10.1007/S10551-013-1748-5/TABLES/5.

29.

Hastalona

Sadalia

Literature Review ESG and Sustainability Finance. Budapest International Research and Critics Institute (BIRCI-Journal): Humanities and Social Sciences, Vol. 4, No. 3, 2021, pp. 3548–3557. https://doi.org/10.33258/BIRCI.V4I3.2122.

30.

Elkington

Towards the Sustainable Corporation: Win-Win-Win Business Strategies for Sustainable Development. California Management Review, Vol. 36, No. 2, 1994, pp. 90–100. https://doi.org/10.2307/41165746.

31.

Global Reporting Initiative. GRI - Standards. https://www.globalreporting.org/standards/. Accessed August 30, 2022.

32.

Pires

S. P.

Sénéchal

Loures

E. F. R.

Jimenez

J. F.

An Approach to the Prioritization of Sustainable Maintenance Drivers in the TBL Framework. IFAC-PapersOnLine, Vol. 49, No. 28, 2016, pp. 150–155. https://doi.org/10.1016/J.IFACOL.2016.11.026.

33.

Global Reporting Initiative. GRI - Mission & History. https://www.globalreporting.org/about-gri/mission-history/. Accessed August 30, 2022.

34.

Marete

C. K.

Incorporating Sustainability Planning in Airport Master Plans: A Case Study of Six U.S Small Hub Airports. School of Aviation & Transportation Technology, West Lafayette, IN, 2019. https://doi.org/10.25394/PGS.8072012.v1.

35.

Kuzey

Uyar

Determinants of Sustainability Reporting and Its Impact on Firm Value: Evidence from the Emerging Market of Turkey. Journal of Cleaner Production, Vol. 143, 2017, pp. 27–39. https://doi.org/10.1016/J.JCLEPRO.2016.12.153.

36.

Global Reporting Initiative. Consolidated Set of the GRI Standards. GRI, Amsterdam, The Netherlands, 2022.

37.

Neuman

W. L.

Social Research Methods: Qualitative and Quantitative Approaches. Pearson Education Limited, Harlow, 2014.

38.

Yin

R. K.

Case Study Research: Design and Method. Sage, Thousand Oaks, CA, 2018.

39.

Shay

L. A.

Results of Aviation Week’s Biennial Top 10 MRO Survey. Aviation Week Intelligence Network. https://aviationweek.com/mro/results-aviation-weeks-biennial-top-10-mro-survey. Accessed September 13, 2022.

40.

Chakravarty

World’s Top 10 Commercial Aviation MRO Companies. Market Research Reports® Inc. Market Research Reports, Inc. https://www.marketresearchreports.com/blog/2020/01/21/world%E2%80%99s-top-10-commercial-aviation-mro-companies. Accessed September 13, 2022.

41.

Henneberry

Top MRO Suppliers and Companies in the USA. Thomasnet.com®. https://www.thomasnet.com/articles/top-suppliers/mro-suppliers-and-companies/. Accessed September 13, 2022.

42.

Verified Market Research. World’s Top 7 Commercial Aviation MRO Companies. VMR. https://www.verifiedmarketresearch.com/blog/worlds-top-commercial-aviation-mro-companies/. Accessed September 13, 2022.

43.

ST Engineering. ST Engineering Sustainability Report 2021. https://www.stengg.com/en/sustainability/sustainability-reports/sr2021/. Accessed September 27, 2022.

44.

HAECO. HAECO: Sustainable Development. https://sd.haeco.com/en/sd-management-approach/sd-policy/. Accessed September 27, 2022.

45.

AAR CORP. Environmental, Social, and Governance (ESG). AAR Corporate. https://www.aarcorp.com/en/about/environmental-social-and-governance-esg/. Accessed November 1, 2022.

46.

SIAEC. Sustainability Report 2020/2021. https://www.siaec.com.sg/pdf/SIAEC_SR_FY2020-21.pdf. Accessed September 27, 2022.

47.

ST Engineering. 2018 GRI Content Index. https://www.stengg.com/media/617692/gri-content-index-2018.pdf. Accessed November 25, 2022.

48.

HAECO. 2021 Sustainable Development Highlights. https://sd.haeco.com/media/t04kk2t1/haeco-group-sd-report-2021_en_compressed.pdf. Accessed September 27, 2022.

49.

SIAEC. Sustainability Report 2017/2018. https://www.siaec.com.sg/pdf/SIAEC_SR_FY2017-18.pdf. Accessed November 25, 2022.

50.

SIAEC. Sustainability Report 2018/2019. https://www.siaec.com.sg/pdf/SIAEC_SR_FY2018-19.pdf. Accessed November 25, 2022.

51.

AAR CORP. 2021 Environmental, Social and Governance Report. https://www.aarcorp.com/assets/3/7/AAR%20ESG%20report%20082321%20final.pdf. Accessed September 27, 2022.

52.

ST Engineering. Risk and Sustainability Highlights 2016. https://www.stengg.com/media/30875/2016-sustainability-report.pdf. Accessed November 25, 2022.

53.

ATAG. Aviation Supporting the UN Sustainable Development Goals: Aviation: Benefits Beyond Borders. https://aviationbenefits.org/un-sustainable-development-goals/. Accessed November 15, 2022.

54.

ICAO. Aviation’s Contribution Towards the United Nations 2030 Agenda for Sustainable Development. International Civil Aviation Organization, Montreal, Canada, 2019.

55.

Swastanto

G. A.

Yother

Johnson

Student Paper: Engine Wash and Sustainability in an Engineering Technology. Proc., ASEE Annual Conference & Exposition, Minneapolis, MN, 2022.

56.

United Nations. The 17 Goals. Sustainable Development. https://sdgs.un.org/goals. Accessed November 15, 2022.