Assessing airline communication for voluntary carbon offsets

Air transport plays a significant role in climate change, contributing two percent of global carbon emissions in 2022, with its emission growth outpacing that of other transportation sectors¹. Studies also revealed that air travel contributes about four percent to human-induced global warming due to high altitude emissions and pollutants beyond carbon dioxide (CO₂)^2,3,4,5. To reduce emissions, flying less stands out to be the most efficient means, yet it seems improbable from the viewpoints of both travellers and airlines⁶. While technical advancements for sustainable aviation fuels (SAF) and fuel efficiency are in progress, they still fall short of aligning the aviation industry with the goal of achieving net-zero emissions by 2050¹.

Rather than directly reducing emissions, airlines often adopt consumer-based approaches such as voluntary carbon offsetting (VCO) programmes, allowing travellers to learn about and compensate their flight emissions. However, VCO programmes have come under increasing scrutiny for potentially misleading communication and lack of transparency. Following the March 2024 court ruling on KLM’s marketing practices, which found their VCO claims to be misleading, the European Commission and EU consumer authorities demanded that 20 airlines address similar issues in their VCO and SAF programmes⁷. This reflects a broader concern that many airlines’ communications may create an impression of environmental responsibility without fully disclosing the limitations and complexities of carbon offsetting.

Despite such regulatory attention, a significant gap remains in the absence of a standardized framework for assessing airline VCO communications, making it challenging to consistently assess the trustworthiness of these programmes across the industry. Previous studies highlight issues with transparency but often omits which types of information airlines should disclose or clear metrics for measuring transparency. Moreover, limited attention is given to the other features needed in VCO communication, such as accessibility and ease of purchase. Addressing these gaps is crucial to help airlines adopt best practices.

This study first conducted content analysis to examine whether and how airlines offered carbon offset options and portrayed VCO on their websites. Data collection and analysis were conducted between late 2023 and early 2024. Recognising that customer perception is a key outcome of corporate communication, we obtained a list of 32 airlines for analysis from the Skytrax World Airline Awards 2023, where winners were determined by global traveller votes. These airlines included 12 from Asia (two from the Middle East), 10 from Europe, and 10 from North America. To conduct the analysis, we developed a coding scheme to categorise information based on accessibility, transparency, and flexibility. Additionally, this study employed interpretive analysis to identify misleading practices in airline VCO communication, based on a greenwashing assessment framework^8,9 By applying this dual approach, we aim to provide a comprehensive understanding of how airlines communicate their VCO programmes. Notably, this study focuses solely on communication strategies and does not assess the effectiveness of VCO programmes.

Since its introduction, carbon offsetting has faced criticism for allowing buyers to maintain or even increase emissions while feeling less accountable for their environmental impact¹⁰. NGOs, journalists, and researchers have highlighted shortcomings in offset projects, such as land conflicts, human rights violations, and exaggerated claims about carbon reduction effectiveness^11,12,13. “These documented issues cast doubt on the credibility and effectiveness of carbon offset projects. Despite the criticism, the voluntary carbon market continued to expand and enjoyed an exponential growth in the early 2020 s^14,15. This surge was driven by increasing pressure on corporations to meet sustainability commitments and a growing awareness of climate change among consumers and businesses¹⁶. The aviation sector, in particular, leaned into VCO as a visible step to mitigate emissions amid slow advancements in alternative fuels and technologies. Industry bodies like the International Air Transport Association (IATA) endorsed the use of carbon offsets as a bridge solution¹⁷, while the ICAO’s Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) provides the framework to standardise and enhance emissions management practices for the sector.

According to a recent review¹⁸, over seventy scholarly works on airline VCO programmes have been published in the past twenty years, with most research focusing predominantly on quantitative analyses of the sociodemographic attributes and behavioural drivers of those who purchase offsets. Researchers have explored the factors influencing these decisions¹⁹, emphasizing aspects such as demographic profile²⁰, environmental knowledge²¹, social norms²², offset project attributes²³, and perceptions of different message strategies²⁴. Despite geographical variance, the purchase rate of VCO has been generally low, coupled with low awareness of such programmes^20,25. A study found that only about seven percent of respondents purchased VCO, with less than one-third having heard of the programmes in Germany²⁶. However, there has been few research on how VCO programmes contribute to broader aviation sustainability efforts.

With growing scrutiny on climate-related greenwashing²⁷, some studies have turned to examine airlines’ communication about VCO, especially concerning transparency and credibility^6,28,29. Yet, the literature remains surprisingly limited¹⁶. One seminal contribution is from Guix et al. (2022), who developed a coding framework to evaluate VCO communication by categorizing claims into trustworthy or misleading types and natures²⁸. Their study analysed 37 airlines and found that 44% of their claims were misleading, often using tactics such as “vagueness,” “lesser of two evils,” and “no proof.” They noted that these misleading claims often involved omitting critical information about the offsetting process, the quality of offset projects, and their real-world effectiveness. Such omissions led to significant gaps in transparency and ultimately created confusion for air travellers attempting to make informed choices. Conversely, the study found that claims focused on processes and facts were generally more reliable, as they were easier to verify through available data and clear references. This blend of reliable and misleading communication posed challenges for consumers, who might struggle to discern which claims were trustworthy.

Similarly, Mello & Rosario (2024) assessed the authenticity and alignment of VCO claims among European airlines under the EU’s greenwashing regulations²⁹. Their analysis highlighted that many airlines engaged in greenwashing, evidenced by the superficial and strategically positioned nature of VCO programmes that prioritized brand image over environmental commitment. They also pointed to the insufficient regulatory frameworks that fail to effectively identify and prevent greenwashing practices in the industry, which allows misleading communication to persist. The findings underscored the need for comprehensive regulations to ensure transparency and consistency in how airlines present their VCO programmes.

Our article aims to advance the research on airlines’ communication regarding VCO programmes. While prior studies have highlighted issues such as misleading claims and the strategic use of VCO for brand management, our research suggests a more interactive view to also include how easily travellers can find, understand, and engage with VCO-related information²⁷. We thus assess key dimensions like accessibility, transparency, and flexibility in airline communications, emphasizing not just the content provided but also the user experience. Additionally, our study incorporates a broad regional analysis that includes airlines across Asia, Europe, and North America. We also address the evolving trend of airlines shifting towards SAF options and examine the role of third-party VCO partners in influencing the quality and transparency of these programmes. By analysing these aspects, we aim to provide deeper insights into how airlines convey environmental responsibility and how these communication practices may shape consumer perception and policy implications.

Our analysis began by identifying the patterns of how airline VCO programmes are offered. As Fig. 1 shows, among the 32 airlines, twenty-one offered VCO programmes either as standalone options or combined with SAF purchase choices. The rest of the eleven airlines—including Air France and United Airlines shifted only to SAF^30,31—did not offer any VCO options and thus we dropped them in the subsequent analysis. Figure 2 presents the findings on accessibility, transparency, and flexibility, as evaluated through the coding scheme. Please note that, in this part, we focused solely on identifying and categorizing the information provided by the airlines, without assessing the accuracy or potential misleading nature of their claims.

. Green cells represent airlines with a VCO programme. Yellow cells indicate airlines with a VCO programme integrated with SAF options. Grey cells show airlines without a VCO programme.

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. The upper section presents a matrix summarising the availability of specific programme features and information (coding items). Green cells indicate presence and grey cells represent absence, while the totals show how many airlines fulfilled each coding item. The lower part details the coding item list under three dimensions: accessibility, transparency and flexibility.

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Accessibility: lack of prominent placements

The first dimension of our coding scheme is the accessibility of VCO programmes, including placement within homepages and ticket booking process (A1 to A5). Seventeen airlines had a dedicated VCO programme webpage, either embedded with a payment gateway or redirected customers to a third-party website for offset purchases. However, only six airlines provided direct links to the VCO programmes on their homepages or sustainability/ESG pages, often placing them within menus, dropdown lists and banners. Furthermore, only three airlines offered the option to purchase offsets during flight ticket booking. This lack of prominent placement suggests that many airlines may not prioritize VCO programmes, and as a result, air travellers may remain unaware of these programmes unless they actively seek them out.

Transparency: incomplete programme and offset project information

In our coding scheme, transparency was evaluated based on two categories: general VCO programme information (T1–T5) and offset project details (T6–T10). While all airlines provided an introduction to carbon offsetting, and seventeen explained the emissions calculation methods, only seven airlines addressed the climate impact of aviation. Nevertheless, all of these aspects showed significant variations in the extent of information disclosure, descriptions, and terminology (see Misleading Communication). Moreover, regarding the effectiveness of their VCO programmes, only seven airlines reported the quantity of offsets purchased by customers and/or the number of participants, providing cumulative totals, figure of the reporting year, or both.

Transparency in offset project details was notably insufficient. Our analysis considered only project-specific information, excluding general statements. Sixteen airlines provided project locations and brief descriptions, sometimes including project types, associated social benefits, and the related Sustainable Development Goals. However, only thirteen airlines listed project names, while others grouped projects by type or location, and specified the certification bodies for each project. Ultimately, only eleven airlines (55 percent) collectively disclosed all four essential details – project names, locations, certification bodies and descriptions, and even fewer (seven) airlines offered external links to certification body websites for further project details. Without a comprehensive disclosure, travellers would not be able to verify the credibility of the projects they opt to support.

Flexibility: limited offset project selection

VCO programmes often involve a portfolio of offset projects pre-selected by airlines, with varying quality and co-benefits. Ideally, travellers should have the option to choose offset projects that align with their priorities. However, only three airlines offered this choice, indicating that flexibility in offset project selection is uncommon and that airlines may not prioritize travellers’ preferences. Notably, Air Canada allowed offset project selections only for members redeeming points in exchange for carbon offsets on a separate website of the official e-store, apart from the VCO programme page.

Patterns in programme characteristics

Regional variations

In Europe and North America, as Fig. 1 shows, airlines have either discontinued or revamped their VCO programmes to incorporate SAF options. Of the eight European airlines offering VCO programmes, six also offered SAF options, with Air France completely transitioning to SAF programme. Similarly, three of six North American airlines integrated SAF options with VCO programmes, while United Airlines also entirely switched to SAF programme. Conversely many Asian airlines have never offered VCO in the operation and none has combined VCO with SAF options.

Public scrutiny over carbon offsets, particularly in Europe and America, has intensified due to concerns about exaggerated climate benefits and negative social impacts^32,33. In contrast, supporting SAF is seen as more advantageous for airlines, supported by mandates such as the ReFuelEU Aviation which requires increasing the SAF blending amounts³⁴. However, the cost of SAF – 120 percent to 700 percent higher than fossil-based jet fuel³⁵– remains a significant barrier, despite financial incentives and regulatory support from the EU’s Emissions Trading System (EUETS) and CORSIA³⁶. These developments may explain why European and North American airlines are shifting towards SAF, while their Asian counterparts lag in this regard.

VCO Programmer Partners: In total, seventeen airlines disclosed their VCO programme partners. While eight partnered with CHOOOSE, a climate solutions provider headquartered in Norway, and two from the same group with Compensaid, other airlines worked with Tasman Environmental Markets, blue dot green, Climate Impact Partners, Semtrio, Cool Effect, FORLIANCE and Carbonfund.org.

Airlines partnering with CHOOOSE generally provide more detailed project information but often neglect prominent website placements and options for choosing projects. For example, while all CHOOOSE-partnered airlines specified project names, locations, and details, none offered purchase options during ticket booking. Conversely, airlines partnering with other agencies tend to offer less transparency. Therefore, partners do not guarantee an accessible, transparent, or flexible VCO programme.

Project Attributes: Sixteen airlines (80 percent) disclosed the types and locations of each offset project, ranging from two to thirteen projects per airline. Nearly half were land use and forestry projects, with others including cleaner stoves, renewable energy, biogas, biochar, water, waste-to-energy, and technology. Seventy-three percent of projects were in developing countries.

Fourteen airlines specified the certification programme of each offset project. Among these, thirty-six percent were certified by the Gold Standard, seventeen percent had dual accreditation from VCS and the Climate, Community and Biodiversity Alliance (CCBA), and nine percent were certified by VCS. Other certifications included puroearth and local registries such as J-Credit and BC Carbon Registry. Ten projects, from Turkish Airlines, Swiss International Air Lines and Lufthansa, were labelled with “VCU” or “VER” without specifying certification programmes. While “VCU” typically refers to VCS carbon credits, “VER” represents general “Voluntary Emissions Reductions” which are carbon credits that can be issued by various certification standards.

Misleading communication

Going beyond the earlier part of the study, we conducted an interpretive content analysis to identify misleading tactics and compare the information provided by airlines. The following section presents these observed tactics, with selective examples shown in Table 1, followed by an analysis of content variations across airlines.

In our observation, misleading tactics involving factual omission and distortion were more common, while factual denial was less prevalent, likely due to the strong scientific consensus on climate change and increased scrutiny from the public. It is also important to note that some information may fall under multiple misleading tactics.

Carbon offsetting is a complex mechanism, particularly within the unregulated voluntary market, which faces significant challenges in credibility and effectiveness in addressing climate change. A clear and neutral introduction is essential. However, paltering—a tactic that involves presenting a “half-truth that sends the wrong impression”⁹—was observed in how carbon offsetting and VCO programmes were presented. For instance, ANA All Nippon Airways highlighted the certification programmes of their offset projects to emphasise quality, yet omitted well-documented shortcomings:

“ANA offers the highest standards of quality—the same can be said of the selection of climate protection projects that it offers. Both selected projects are certified and one of them is already registered under the VCS-CCB and Gold Standard. The VCS Program is the world’s most widely used voluntary GHG program. The Gold Standard is an independently managed label, provided to honour superior climate protection project standards, and the emission reduction certificates that are generated from them.”

While this description highlights the widespread use of the VCS, it neglects the criticisms such as overestimated carbon reductions and negative social impacts, especially in forestry projects^11,12,13. This selective presentation can mislead customers about the effectiveness of their carbon offsetting efforts.

Moreover, terms such as “honour” and “superior” can convey an exaggerated sense of excellence and reliability, which may not be guaranteed given the complexity of carbon offsetting. By glossing over the complexities and limitations of carbon offsetting, the airline potentially misleads customers with an overly positive impression.

The quantity of carbon offsets purchased by air travellers is typically based on airline-provided emission calculators. However, selective disclosure in these calculations can be misleading. EVA Air, for example, claimed to use real flight data to estimate CO₂ emissions but omitted important details such as the number of flights, emission factor sources, and whether non-fuel-related emissions were included. It also ignored significant contributors like nitrogen oxides and water vapour. Labelling the outcome as “climate impact” is thus misleading, as it fails to account for the full range of aviation’s environmental effects.

Vagueness, common in green marketing, was another issue. Some airlines used ambiguous terms including “eco-friendly”, “environmentally friendly”, “high-impact” and “high-quality” to describe their VCO programmes without clear explanations. Additionally, terms such as “net-zero” and “carbon neutral” were often employed to convey a green image and the effectiveness of carbon offsetting, yet lacked proper definitions or explanations. Despite the growing popularity of net-zero and carbon neutrality, there are no universal definitions or guidelines for these claims. Without specificity, it is difficult for travellers to understand their actual meaning, leading to potential misinterpretation and misleading impressions.

Additionally, airlines often use terms such as “zero emissions” and “zero-carbon travel,” which falsely suggest that their flights produce no emissions at all. This representation is misleading because offsets do not eliminate emissions generated during flights; they only compensate for a portion of these emissions by funding projects elsewhere. Moreover, most airline emissions calculations typically focus solely on fuel consumption and exclude non-CO₂ emissions, such as water vapour and nitrogen oxides, which contribute significantly to warming. This exclusion suggests that the actual environmental impact may be underestimated when considering the broader range of emissions associated with air travel.

It is important to note that not all instances of vague or selective communication may be deliberate. Some airlines may face challenges due to the lack of comprehensive industry standards or clear guidelines for presenting complex environmental data. Additionally, airlines operate within a landscape where the complexities of carbon accounting and the evolving nature of certification standards can make clear communication difficult.

Apart from identifying misleading practices, it is crucial to provide a comprehensive understanding of the current landscape across airlines and highlight areas for improvement. The following paragraphs offer an in-depth analysis of the observed content variations in airline communication regarding VCO programmes.

The analysis below does not endorse any of the examples as the best practices, but it highlights the varying levels of transparency and clarity in airline VCO communication. Tables 2, 3 list the descriptions provided by airlines in their introductions to carbon offsetting or VCO programmes and the climate impact of aviation respectively.

Airlines such as EVA Air, China Southern Airlines, Austrian Airlines, Swiss International Air Lines and JetBlue Airways emphasised an oversimplified view of carbon offsetting by suggesting that offsetting alone can achieve “zero-carbon travel”, “carbon neutral flight”, and “more sustainable” flights. In addition to using inappropriate terms without clear explanations, these statements potentially mislead air travellers by omitting the actual complexity and limitations of carbon offsetting.

Conversely, KLM and British Airways acknowledged the limitations of carbon offsetting, clarifying that it would not eliminate flight emissions or environmental impacts, but rather serve as a supplementary measure. These statements provided a more realistic view of carbon offsetting. KLM’s use of the term “nature regeneration” to represent its VCO programme might lead to some misunderstanding about the full scope of its environmental benefits; British Airways presented a more neutral view on the role of participating in VCO programmes as a way to support environmental projects.

Most airlines addressed the climate impact of aviation in the “Frequently Asked Questions” section on their websites. Airlines such as Singapore Airlines and ANA All Nippon Airways referenced data from the Intergovernmental Panel on Climate Change, emphasising that aviation contributes around two percent of global greenhouse gas emissions. Notably, KLM, Swiss International Air Lines, and British Airways did not quote data from external organisations. KLM focused solely on CO₂ emissions, and while Swiss International Air Lines acknowledged that the climate impact of aviation was not limited to carbon emissions, it did not provide further explanation. British Airways stood out by addressing the concept of radiative forcing, which is commendable given that many airlines do not mention these additional climate effects at all. However, their use of a radiative forcing index of 1 created an impression of considering this factor without reflecting it in actual emissions calculations.

This study highlights the complexities and challenges of airline communication regarding VCO programmes, revealing diverse practices and significant regional variation across the industry. While prior studies have highlighted issues of misleading communication, our research extends these findings through a comprehensive coding scheme that captures critical dimensions of accessibility, transparency, and flexibility in VCO programme communication. Through analysis of 32 airlines, the results show a range of communication approaches: some airlines prioritize transparency and detail, while others use vagueness, selective disclosure, or exaggeration. Our interpretive analysis supports earlier findings that misleading claims, while may not be widespread, do exist and deserve attention. These include incomplete disclosures and overstated terms that can mislead consumers about the actual impact of carbon offsetting.

The study also notes that some airlines have quietly discontinued VCO programmes or shifted to SAF, while others never implemented such programmes. This diversity underscores the evolving landscape, as airlines explore different pathways to balance environmental responsibility with consumer expectations. European and North American airlines are leading the integration of SAF alongside VCO, while many Asian airlines continue to focus on offset programmes. These findings highlight the dynamic progression in this area and suggest a need for flexible yet robust regulatory frameworks to guide transparent and effective communication as the industry evolves.

In recent years, lawsuits have been filed against airlines over misleading environmental claims associated with VCO, yet these cases primarily referenced local laws applicable to general business conduct. Delta Air Lines, for example, was sued under California’s Unfair Competition Law, False Advertising Law, and Consumers Legal Remedies Act³⁷, with only the last one allowed to proceed by the court. The KLM case was based on the Advertisement Code Commission of the Netherlands³⁸, while the lawsuit against United Airlines was filed under the Consumer Protection Act of Maryland³⁹.

Following the court finding of KLM’s misleading marketing campaign in March 2024, the European Commission and EU consumer authorities requested 20 airlines, to address potentially misleading claims about VCO and SAF programmes⁷. These claims included the use of misleading terms, such as “sustainable” and “green”, and the creation of misleading impressions that supporting climate projects could reduce flight emissions. This action was based on the Unfair Commercial Practices Directive following the adoption of the Empowering Consumers Directive in February 2024. In the United States, California has established significant disclosure requirements for businesses engaging in voluntary carbon markets, reflecting the increasing awareness of the need for adequate disclosures about VCO. Effective from January 2024, the Voluntary Carbon Market Disclosures Act enacted by California mandates businesses to disclose specific information about the offset projects they market, sell, or use for claims such as “net-zero”, and “carbon neutral” on their websites⁴⁰.

The effectiveness of these new regulations warrants further study, including whether they will prompt businesses to drop VCO or adopt more transparent practices. In the meantime, robust regulations are crucial to guide airlines in clearly conveying the complexities and limitations of VCO programmes, ultimately facilitating travellers to make informed decisions. To accelerate the progress of combating climate change, carbon offsetting must be used responsibly.

This study adopts content analysis to examine patterns and variations in airline VCO communication and identify misleading practices. As we focus on airlines’ communication with customers, we draw from four lists of the Skytrax World Airline Awards 2023, where winners were determined by global traveller votes for the best airlines. These lists included the “World’s Top 10 Airlines of 2023”, and the regional categories: “Best Airlines in Asia 2023”, “Best Airlines in Europe 2023”, and “Best Airlines in North America 2023”, to maintain a regional focus for comparison. The final set of airlines comprised thirty-two airlines, twelve from Asia, including two from the Middle East, ten from Europe, and ten from North America.

The following procedures were applied to identify relevant content and create a database. The analysis began by identifying airlines that offer VCO programmes. Keywords such as “carbon offset”, “offset”, and “carbon credit” were searched on the airlines’ official websites to determine whether they provided VCO programmes. In cases where no relevant information was found, a supplementary Google search was conducted to confirm the availability of VCO programmes. If the results were negative, the airlines were classified as not currently providing VCO programmes; if positive, they were classified as providing such programmes. However, if an external source stated that the airline provided a VCO programme but no purchase channel was identified, the airline was classified as not providing VCO programmes. Data collection from websites occurred between late 2023 and early 2024.

Further content analysis focused on their official websites, including those co-hosted with programme partners, but excluding external websites hosted entirely by third parties. The latest standalone sustainability reports available on airlines’ official websites were examined, and if unavailable, the most recent annual reports were also reviewed. Analysis was conducted only on English-language materials to ensure consistency and comparability, as English is the common language across all airline websites. Consequently, if an airline’s reports were only available in other languages, that airline was excluded from the analysis using the coding scheme to ensure impartiality. Content relevant to VCO found in the abovementioned materials was extracted in paragraphs to a spreadsheet for further analysis.

We developed a coding scheme to classify relevant content across three dimensions: accessibility, transparency, and flexibility. These dimensions were informed by a study that highlight the general low awareness and limited transparency in airline VCO programmes²⁶, as well as broader discussions on greenwashing^8,9,27,41. Literature has emphasized that publicity, and by extension accessibility, along with transparency are the two foundational ideas of democratic communications⁴². Furthermore, studies on consumer preferences demonstrate that choice and personalization—central to the “flexibility” dimension—enhance trust and satisfaction in environmental programs^23,24,25. This scheme functions both as a checklist of essential elements airlines should provide, and as a tool to identify patterns and variations in VCO communication. It focuses on the availability of features and information over content quality. Detailed explanations of the rationale and coding labels for each dimension are provided below.

Accessibility stands as the foremost imperative, denoting the ease with which travellers can access information about VCO programmes. Accessibility builds on the concept of publicity by not only requiring that information is made visible but also ensuring it is structured and presented in a way that facilitates consumer engagement. High accessibility is essential as it represents the first step for air travellers to learn about VCO programmes before purchasing offsets, and influences subsequent consumer engagement with programs¹⁰. The coding labels A1 to A5 assess the presence of a dedicated programme webpage and prominent placements within homepages, sustainability webpages, reports and during flight ticket booking process.

Transparency is a cornerstone of effective environmental communication and corporate accountability. Literature on greenwashing and corporate social responsibility emphasizes that transparency is essential for enabling consumers to evaluate environmental claims critically^27,41. In terms of VCO, transparency is crucial for air travellers to make informed decisions about offsetting. The coding labels T1 to T10 evaluate the availability of two information categories: T1 to T5 cover general information about offsetting, aviation climate impact and programme details, while T6 to T10 focus on offset projects, including their names, locations, types and certification programmes. For example, Air Canada’s explanation of carbon offsetting was categorised as T1:

“Carbon offsetting enables organizations or individuals to take climate action by voluntarily supporting certified third-party projects that contribute to the reduction, avoidance, or removal of GHG emissions.”

The quality of offset projects can vary significantly based on project types, design, methodology, actual implementation and evaluation. Providing details about the selected offset projects is therefore critical for identifying their quality and enabling information cross-checks. Additionally, increasing transparency makes it more likely that airlines and their programmer partners will be more careful in selecting offset projects. General statements, such as Cathay Pacific’s broad claims about project certification, were excluded from this analysis in favour of specific data:

“All of the projects we offer are certified under the Gold Standard to ensure that they are verifiable, credible and make a difference to local communities and the environment.”

Flexibility, the final dimension of the coding scheme, refers to the options available to travellers in selecting carbon offset projects for purchase. This is crucial, especially when pre-selected portfolios include low-quality projects that fail to meet fundamental criteria such as additionality and permanence. In the context of consumer interaction with VCO programmes, flexibility in choosing offset projects can empower travellers, giving them a sense of control and trust in the offsetting process. It also allows consumers to align their purchases with personal values or preferences, such as supporting local projects or initiatives that prioritize biodiversity or social co-benefits. As recent research shows, travellers are more likely to opt in the programme when they are allowed to choose their preferred carbon offset methods⁴³. These three dimensions are interconnected in a way that flexibility is meaningful only when accessibility and transparency are first ensured.

Further analysis was conducted based on the coding scheme results to identify key characteristics and patterns in VCO programmes, including regional differences, potential influence from programme partners and attributes of carbon offset projects selected by airlines.

In the interpretive content analysis, we applied a greenwashing assessment framework^8,9 to identify misleading tactics as a potential indicator for corporate greenwashing. The framework categorises tactics into three types: factual omission, factual distortion, and denial. These tactics span both communication and practices at the organisational level, as well as at the product level. “Factual omissions”, where material information is not disclosed, include tactics such as “selective disclosure”, “over-indexing” and “core business omission” are included. “Factual distortions”, involving claims that are “twisted, unfounded, or exaggerated”, encompass tactics including “no proof”, “empty claims”, “vagueness”, “misleading symbols”, “paltering” and “jargon”. “Denial” tactics involve rejecting established climate science, using “lies and irrelevancies”, and employing “political spin” to lobby against environmental policies. This study focuses on airline communication on VCO programmes only, and thus tactics related to contradictions between actions and communication, such as political spin and the progress of carbon reductions, are excluded in our analysis.

In addition to identifying misleading tactics, we conducted a comparison of the information provided by airlines on carbon offsetting, or VCO programmes, and the aviation climate impact. The analysis sought to highlight the varying degrees of transparency and clarity across different airlines, focusing on the extent of information disclosed and the terminology used, instead of endorsing any particular airline.

While this study provides valuable insights, several limitations should be noted. First, the focus on 32 airlines from Asia, Europe, and North America may overlook practices and trends in other regions. Second, the analysis was conducted primarily in English to ensure consistency, which may have excluded relevant information available in other languages or missed nuances in translation. Additionally, the rapidly evolving regulatory landscape for carbon offsetting and environmental communication, particularly in Europe and North America, poses a challenge. The study reflects the state of regulations at the time of analysis, but future changes could impact airline communication practices regarding VCO programmes. Lastly, many travellers book their tickets through third-party travel agencies rather than airline websites, and this study did not examine how VCO options are presented in those contexts.