Perspectives on Audit Opinions and Key Audit Matters in the Global Airline Industry and the COVID-19 Pandemic

Abstract

The present study investigates whether the COVID-19 pandemic had a negative effect on audit opinion and led to differences in the composition of key audit matters (KAMs) observed in the airline industry. This study uses a sample of 55 airlines whose financial statements are based on International Financial Reporting Standards (IFRSs) and whose financial statement audit follows National or International Standards on Auditing (ISAs) for audit opinion, as well as a sample of 42 airlines whose financial statements are based on IFRSs and whose financial statement audit follows ISAs for the composition of KAMs. A textual analysis, a content analysis, a frequency distribution, and a chi-square test were conducted for the periods before, during, and after the COVID-19 pandemic. The findings reveal that the COVID-19 pandemic had no significant effect on audit opinion, except for one airline whose audit report declared a disclaimer of opinion. In contrast, the impairment of goodwill and intangible assets (as an industry-specific KAM) and going concern (as a KAM specific to the COVID-19 pandemic) were the two KAMs that were typically observed during the COVID-19 pandemic due to increased uncertainty. This was found to be the case, even though the main KAMs in the airline industry are usually revenue recognition; lease accounting; property, plant, and equipment (PPE); and hedge accounting. This study contributes to the debate on the effect of the COVID-19 pandemic on audit opinions and KAMs by offering evidence from the underexplored airline industry.

1. Introduction

The airline industry comprises several businesses. It not only includes airfreight operations in the context of passenger flight and air cargo services, but also substantially contributes to economic growth through aircraft manufacturing, tourism, employment, prosperity, supply chain management, innovation, cooperation, and global trade (Çelik, 2017; Tay et al., 2020).

Despite making significant contributions to economic growth, the airline industry is influenced by several external factors, such as public health threats, that not only affect its functioning and profitability, but also its sustainability (Tay et al., 2020). Without the environmental screening of these factors, it is impossible to run an enterprise operating in the airline industry effectively and efficiently (Brown & Kline, 2020). These external factors (also called exogenous shocks (Brown & Kline, 2020; Dube et al., 2021), endogenously driven factors (Renold et al., 2023), environmental shocks (Linden, 2021), external challenges (Dube et al., 2021), external business threats (Dube et al., 2021), or exogenous impacts (Renold et al., 2023)) affecting the aviation industry include (a) climate change, (b) trade disputes, (c) diseases and pandemics, and (d) geopolitical conflicts (Zhang et al., 2024). The vulnerability of the industry to unexpected shocks has been verified through analyses of these factors.

Within the framework of these external factors, the following events have dramatically affected the airline industry: the 1973 oil crisis, the Iran–Iraq War in the early 1980s; the Gulf Crisis in the early 1990s; the 1997 Asian Financial Crisis; the 9/11 terrorist attacks in 2001; the financial crises that took place in 1998, 1999, and 2008; and natural shocks such as Eyjafjallajökull (the volcano in northern Europe) or the Indonesian volcano ash clouds (Linden, 2021; Dube et al., 2021; Renold et al., 2023). Recently, the Russia–Ukraine and Israel–Palestine conflicts have also disrupted flight operations (Zhang et al., 2024).

In the context of diseases and pandemics, the operations of the airline industry have been negatively affected by the outbreaks of numerous epidemics and pandemics: SARS in East Asia in 2003 (Renold et al., 2023); avian influenza H5N1 in 2006; swine influenza H1N1 in 2009; MERS in 2013; and COVID-19 in 2020 (Miani et al., 2021; Dube et al., 2021). SARS had a dramatic impact, with a reduction of 8% in annual Revenue Passenger Kilometers (RPKs) among Asia-Pacific airlines (Miani et al., 2021). However, the impact of the COVID-19 pandemic has been much more severe than that of SARS; by March 2020, a 54.7% reduction in RPKs was observed, compared to 2019, globally.

Due to the COVID-19 pandemic, the following events occurred in the airline industry:

(1)

The airline industry started to operate at a low capacity as of 28 October 2020, compared to 2019. For instance, departure/arrival traffic in Norway, Turkey, France, Germany, and Italy declined by 39%, 52%, 55%, 62%, and 64%, respectively (Dube et al., 2021).

(2)

Revenue generation in the airline industry was negatively affected. For instance, the realized revenue in Europe was as much as 88% lower than the expected revenue in April 2020, and as of June 2020, in Europe, the realized revenue was less than 20% of the expected revenue (Dube et al., 2021).

(3)

Airlines considered restructuring and resizing to prevent cash burns (Dube et al., 2021). In this context, job layoffs, and the retiring of old and large aircraft were considered to increase operational efficiency in the most cost-effective way. For instance, British Airways retired its 31 Boeing B747-400 models in mid-July 2020, four years earlier than the planned retirement date of 2024.

(4)

Mass grounding of aircraft occurred (Dube et al., 2021), and this was mostly observed from March 2020 to June 2020. To find space to park aircrafts at airports became difficult, and this mass grounding led to increased parking fees, mandatory maintenance expenses, and a significant loss of revenue for airlines.

(5)

Several rescue packages for the aviation industry were announced by governments, amounting to USD 123.1 billion in the global context (Dube et al., 2021). These packages include loans, equity financing, ticket taxes, corporate taxes, and fuel taxes. However, 55% of government aid—USD 67 billion out of USD 123.1 billion—consisted of loans, leading to the accumulation of additional debt in the industry. Therefore, the industry’s huge debt structure increased.

The common denominator of these external challenges is an increase in the level of uncertainty in effectively and efficiently managing enterprises operating in the airline industry (Linden, 2021).

Correspondingly, the COVID-19 pandemic also presented an exogenous shock for auditors (Xiang & Ma, 2025). It was outside the control of auditors’ professional responsibilities and activities (Luo & Malsch, 2023), and since the 2007–2008 global financial crises, it has been considered as the most significant event for auditors and their clients (Albitar et al., 2020).

The agency theory defines an audit as a monitoring mechanism that ensures the enhanced communicative value of an audit report (Jensen & Meckling, 1976). The need for a financial statement audit is based on the willingness of managers and shareholders to increase the credibility of the financial reporting process (Hategan et al., 2022), and this mechanism should even work in emergency situations, such as the COVID-19 pandemic.

Auditing regulatory bodies (e.g., the International Auditing and Assurance Standards Board (IAASB) and the Public Company Accounting Oversight Board (PCAOB)) indicated that the COVID-19 pandemic had a significant impact on performing auditing work (Hegazy et al., 2022). The auditing of clients’ financial statements and disclosures became difficult, and the risk of fraud and uncertainty increased based on publicly available information (Hay et al., 2021). The activities of auditors (e.g., audit plans, accounting estimates, assessments of going-concern, and forming audit opinions) were affected and revised (Diab, 2021; Hay et al., 2021; Hegazy et al., 2022) because auditors faced the challenges of asset depreciation, stock valuation, revenue recognition, cash management, and payment of tax liabilities in ensuring the reliability and correctness of financial statements and disclosures (Deb & Chakraborty, 2020). Furthermore, the pandemic made on-site audit impossible (Hegazy et al., 2022; Xiang & Ma, 2025). To obtain audit evidence, auditors utilized alternative auditing procedures (e.g., video technology), which may have increased the risk of fraud (Diab, 2021).

In this context, the objective of this article is to investigate whether the COVID-19 pandemic, an exogenous factor on auditing, had a negative effect on audit opinions, and made a difference on the composition of KAMs declared in the audit reports of airlines, considering the periods before, during, and after the COVID-19 pandemic, within the framework of increased uncertainty during the pandemic period. Therefore, it extends the prior literature on audit opinions and KAMs in the airline industry (Özçelik, 2020; Öztürk, 2022), which concentrate on the period before the COVID-19 pandemic.

2. Literature Review

In line with the objectives of this present article, the literature review on the effect of the COVID-19 pandemic on auditing is divided into three sections: (1) research related to audit opinion and the COVID-19 pandemic in general; (2) research related to KAMs and the COVID-19 pandemic in general; and (3) research related to audit opinion, KAMs, and the COVID-19 pandemic in the airline industry. All three sections consider the periods before, during, and after the COVID-19 pandemic.

2.1. Literature Review on Audit Opinion and the COVID-19 Pandemic in General

By analyzing the published sources discussing the impact of COVID-19 on auditing in New Zealand from March to September 2020, Hay et al. (2021) found that the COVID-19 pandemic was anticipated to significantly influence audit outcomes (e.g., audit opinions). However, the observed impact was far more limited than expected. They found fewer modified audit opinions, fewer explicit mentions of COVID-19 in “emphasis of matter” opinions, and fewer new KAMs within the framework of New Zealand auditing regulations.

2.2. Literature Review on KAMs and the COVID-19 Pandemic in General

Regarding KAMs, the ISA 701 “Communicating KAMs in the Independent Auditor’s Report” defines KAMs as the most significant factor in the audit of the financial statements in the current period, considering the auditor’s professional judgment (IAASB, 2015c). The KAMs in audit reports are communicated for three reasons (IAASB, 2015c): (1) to increase the communicative value of the auditor’s report by improving transparency about the audit that was performed; (2) to provide additional information to the users of the financial statements to assist them in understanding the most significant factors in the audit of these statements in the current period, within the framework of the auditor’s professional judgment; and (3) to assist the users of financial statements in understanding the entity and areas of significant management judgment in the audited statements.

Regarding the accounting literature on the KAMs declared in audit reports during the COVID-19 pandemic, several articles have been published, such as Hegazy et al. (2022), Kend and Nguyen (2022), Hategan et al. (2022), Ecim et al. (2023), Rainsbury et al. (2023), Alharasis et al. (2024), and Alshdaifat et al. (2025).

Hegazy et al. (2022) investigate how auditors’ characteristics (e.g., auditors’ experience, industry specialization, professional qualifications, gender differences, auditor’s position, type of audit firm) affect the KAMs declared in audit reports considering the periods before and during the COVID-19 pandemic. This article states that auditors were more effective in carefully reporting KAMs during the COVID-19 pandemic and provides evidence of certain auditors’ characteristics (e.g., industry specialization, auditors’ experience and qualifications, and auditors’ positions) that are significant in subjective judgment in the audit report process.

Kend and Nguyen (2022) investigate the effect of the COVID-19 pandemic on audit procedure disclosures in the audit reports declared within the KAM section for the years 2019 (before the COVID-19 pandemic) and 2020 (during the COVID-19 pandemic). The sample of this research includes 1600 firms whose shares are listed in the Australian Stock Exchange. Since audit procedure disclosures referencing COVID-19 are of particular interest in this article, the findings reveal the top six KAM topics referencing COVID-19 in audit procedure disclosures: (1) asset valuation, (2) revenue recognition, (3) impairment, (4) goodwill and intangible assets, (5) PPE, and (6) acquisitions.

Hategan et al. (2022) investigate how auditors identified the impact of the COVID-19 pandemic on firms’ 2019 (before the COVID-19 pandemic) and 2020 (during the COVID-19 pandemic) annual financial statements, and considered this impact as a KAM in audit reports (e.g., KAM topics), along with the factors that affected their reporting (e.g., the auditor’s size, frequency of the event, and going-concern uncertainty). The research sample includes 767 companies whose shares are listed in European stock exchanges, and whose KAMs declared in audit reports include the words “COVID-19,” “Coronavirus”, and “pandemic”. Since the composition of KAMs, which includes KAM topics, is of particular interest in this article, 67 KAM topics were considered, of which 47 declared the effects of the COVID-19 pandemic. Within the 47 KAM topics affected by the pandemic, however, 12 topics are relatively significant: (1) going-concern, (2) goodwill and intangible assets, (3) long-lived assets, (4) investment valuation—property, (4) allowance for credit losses, (5) investment valuation—securities and financial instruments, (6) revenue and other income, (7) accounts and loans receivable, (8) significant one-off transactions, (9) inventory, (10) PPE, (11) revenue from customer contracts, and (12) deferred income taxes.

Ecim et al. (2023) analyze the KAMs reported in the audit reports of firms operating in South Africa from 2017 to 2020. The research sample includes 356 listed entities whose shares are traded in the Johannesburg Stock Exchange. Since the composition of KAMs is of particular interest in this article, the findings reveal that the top three KAM topics are (1) business combinations and goodwill, (2) non-financial assets, and (3) financial instruments. They are followed by revenue; taxes; provisions; other issues (e.g., the adoption of new standards, functional currency); complex estimates; going-concern and impact of the COVID-19 pandemic; “systems, control, and governance”; and inventory. In 2020, the highest number of investigations in going-concern and the impact of the COVID-19 pandemic was observed.

Rainsbury et al. (2023) investigated how KAM disclosures in 2020 (during the COVID-19 pandemic) differentiate from KAM disclosures in 2019 (before the COVID-19 pandemic) in New Zealand in terms of the audit firm type, the industry, and accounting standards. The research sample includes the top 50 firms listed in the New Zealand Stock Exchange, and were selected based on market capitalization. Since the composition of KAMs, which includes accounting standards, is of particular interest in this article, the findings reveal that 16 accounting standards were usually observed in 2019 and 2020: IAS 1—presentation of financial statements, IAS 2—inventories, IAS 12—income taxes, IAS 16—PPE, IAS 24—related party disclosures, IAS 36—impairment of assets, IAS 38—intangible assets, IAS 39—financial instruments: recognition and measurement, IAS 40—investment property, IAS 41—agriculture, IFRS 2—share-based payments, IFRS 3—business combinations, IFRS 10—consolidated financial statements, IFRS 5—non-current assets held for sale and discontinued operations, IFRS 9—financial instruments, IFRS 15—revenue from contracts with customers, and IFRS 16—leases. However, the COVID-19 pandemic mostly strongly affected 5 out of 16 accounting standards: IAS 2, IAS 16, IAS 36, IAS 40, and IFRS 15.

Alharasis et al. (2024) empirically investigate the moderating effect of the COVID-19 pandemic on the relationship between KAMs and auditing quality. Correspondingly, it uses the content analysis method to determine levels of KAM disclosure. The research sample includes 157 Jordanian listed firms whose annual reports were analyzed from 2017 to 2022. Considering 5-year observations of 18 KAM topics, covering the years 2017, 2018, and 2019 (before the COVID-19 pandemic), 2020 and 2021 (during the COVID-19 pandemic), and 2022 (after the COVID-19 pandemic), 12 topics are relatively significant: (1) provisions, (2) complex estimates of fair value, (3) impairments, (4) revenue recognition, (5) IFRS 9, (6) inventories, (7) PPE, (8) going-concern and the impact of the COVID-19 pandemic, (9) taxation, (10) goodwill, (11) investments, and (12) accounts receivable.

Alshdaifat et al. (2025) explores the association between KAMs with accrual and real earning management practices for the years 2017, 2018, and 2019 (before the COVID-19 pandemic) and 2020 and 2021 (during the COVID-19 pandemic). The research sample includes 240 industrial firms whose shares are traded in the Amman Stock Exchange in Jordan. Since the extent of KAM reporting is of particular interest in this article, the findings reveal that the KAMs reported before and during the COVID-19 pandemic are the same. The top two KAM topics are accounts receivable and inventories, which are followed by revenue recognition, PPE, investments, insurance, goodwill, pensions, financial assets, and biological assets.

Although the composition of each article’s sample differs regarding the number and industry of firms within the sample, the KAM topics stated by Hategan et al. (2022), Ecim et al. (2023), Kend and Nguyen (2022), Alharasis et al. (2024), Alshdaifat et al. (2025), and the standards declared by Rainsbury et al. (2023) are generally identical. These KAM topics or standards are significant regarding accounting estimates for asset valuations and revenue recognition due to the material uncertainties of the pandemic. However, these findings reflect the overall perspectives of their samples, and do not have a global, industry-specific focus.

2.3. Literature Review on Audit Opinion, KAMs, and the COVID-19 Pandemic in the Airline Industry

In audit-related accounting literature, audit opinion and the composition of KAMs regarding the airline industry have been analyzed by Özçelik (2020) and Öztürk (2022), who contribute to the audit-related accounting literature regarding the airline industry in Turkish and English, respectively. The contribution of Öztürk (2022) has been cited by Mashayekhi et al. (2024) as a paper reviewing the audit reporting practices in a specific industry. Both papers were authored in the pre-COVID-19 pandemic period, and they form the basis of this present study.

The research sample of Özçelik (2020) includes 40 airlines from Europe, Asia, Australia, and Africa whose financial statement audit is based on ISAs, and whose audit reports declare KAMs in compliance with ISA 701, “Communicating Key Audit Matters in the Independent Auditor’s Report”. It analyzes the audit opinion and the composition of KAMs in the airline industry for the years 2017 and 2018.

In contrast to Özçelik (2020), Öztürk (2022) analyzes the audit opinion and KAM composition in the airline industry for the year 2018; however, it depends on two samples. The first sample includes 57 airlines whose financial statements are based on IFRSs and whose financial statement audit depends on national standards on auditing or ISAs. However, its second sample includes 45 airlines whose financial statements are based on IFRSs; whose financial statement audit is based on ISAs; and whose audit reports declare KAMs, in accordance with ISA 701. Other than airlines from Europe, Asia, Australia, and Africa, the sample of Öztürk (2022) also includes airlines adopting both IFRSs and ISAs from the Americas, including Canada and South American countries.

Regarding audit opinion, Özçelik (2020) does not explicitly state the audit opinions declared in airlines’ audit reports, but it implicitly reveals that the audit reports of all airlines issued unqualified audit opinions (unmodified, clean) in the years 2017 and 2018 regarding ISA 700, “Forming an Opinion and Reporting on Financial Statements”, and ISA 705, “Modifications to the Opinion in the Independent Auditor’s Report” (IAASB, 2015a, 2015b), because all the airlines in Özçelik (2020) declared their KAMs. In line with Özçelik (2020), the first sample of Öztürk 2022 also verifies that all airlines’ audit reports issued unqualified audit opinions in the year 2018.

In determining the composition of KAMs observed in the airline industry, Özçelik (2020) only uses the content analysis and frequency distribution parameters. In addition to content analysis and frequency distribution, however, Öztürk (2022) also classifies KAMs observed in the airline industry as main, rare, and very rare. For this, it determines a certain threshold, namely, the number of regions observed per KAM, within the framework of the number of annual observations by considering the key airline-industry-related accounting topics (Lavi, 2016). The main KAMs consist of industry-specific matters observed in the airline industry, and they are observed in at least four regions globally. For the year 2018, these matters are based on 70% of observations. Thereafter, rare KAMs consist of industry-specific matters and some airline-specific matters observed in the airline industry, and they are observed in two or three regions globally. For the year 2018, these matters are based on 20% of observations. Finally, very rare KAMs are usually airline-specific matters observed in the airline industry, and they are observed in one region globally. For the year 2018, these matters are based on 10% of observations.

In the context of the global composition of KAMs, Özçelik (2020) and Öztürk (2022) find similarly observed KAMs in the airline industry for the years 2017 and 2018. The composition of frequently observed KAMs by Özçelik (2020) includes (a) revenue recognition, (b) lease accounting, (c) PPE items (also called aircraft assets and other PPE items), (d) hedge accounting, (e) intangible assets, (f) deferred tax assets, and (g) litigation and contingent liabilities. However, Öztürk (2022) labels the main KAMs observed in the airline industry as “a”, ”b”, “c”, and “d”, which are industry-specific, in line with Lavi (2016). It labels the rest (“e”, “f”, and “g”) as rare KAMs, of which “e” and “g” are industry-specific matters, and “f” is an airline-specific matter.

In addition, Özçelik (2020) also analyzed the composition of “other” KAMs, in addition to the frequently observed airline-industry-related KAMs for the years 2017 and 2018. The other KAMs declared by Özçelik (2020) usually match with the rare and very rare KAMs declared by Öztürk (2022) in 2018, such as going-concern, employee benefits, retirement obligations, subsidiaries, EU 261 provision, and Brexit, in addition to those mentioned in “e”, “f”, and “g”.

In contrast to Özçelik (2020), Öztürk (2022) also performed a subject-specific content analysis of the main KAMs for the year 2018. For instance, when hedge accounting is the main KAM, its subject-specific content analysis is based on the foreign currency risk, fuel price risk, and interest rate risk observed in the airline industry.

3. Methodology

3.1. Research Sample

This research uses two samples. Firstly, the initial sample represents the airline industry globally, and has been established by 55 airlines whose financial statements adopt IFRSs for the year 2019, and whose financial statement audits are based on national standards on auditing or ISAs. It includes airlines from the Americas (Canada and South American countries), Europe, Middle East and Africa, Asia-Pacific, and Northern Asia and China. Therefore, the airlines represent five regions globally (

Table 1. Composition of the first sample.

Region/Year	2019	2020	2021	2022
Americas	9	9	9	8
Europe	22	22	21	21
Middle East and Africa	8	8	7	7
Asia-Pacific	11	10	11	11
China and Northern Asia	5	5	5	5
Total	55	54	53	52

), in line with Öztürk (2022). This sample is only used for the purpose of analyzing audit opinions in the airline industry from 2019 to 2022. However, the sample size slightly changes from 2019 to 2022 (N₂₀₁₉ = 55 airlines; N₂₀₂₀ = 54 airlines; N₂₀₂₁ = 53 airlines; and N₂₀₂₂ = 52 airlines) due to certain reasons that do not have a major effect on the obtained results, such as the absence of reporting of annual financial statements due to change in reporting dates (e.g., Air Asia X), and due to being non-listed airlines (e.g., Air Partner and Aeromexico).

On the other hand, the second sample includes airlines whose annual financial statements are based on IFRSs, whose financial statement audit depends on ISAs, and whose audit reports declare KAMs, because this sample aims to gather data related to the content of KAMs in the airline industry from 2019 to 2022. It also represents five regions, in line with the first sample (

Table 2. Composition of the second sample.

Region/Year	2019	2020	2021	2022
Americas	3	6	7	6
Europe	17	17	16	16
Middle East and Africa	7	7	6	6
Asia-Pacific	10	9	9	9
China and Northern Asia	5	5	5	5
Total	42	44	43	42

). However, the sample size slightly changes from 2019 to 2022 (N_KAM2019 = 42; N_KAM2020 = 44; N_KAM2021 = 43; and N_KAM2022 = 42) due to certain reasons that do not have a major effect on the obtained results, such as the inexistence versus existence of requirements to declare KAMs in Canada and Portugal; a change in audit regulation from ISAs to PCAOB auditing standards in the United States (US) or vice versa (e.g., Volaris); and the absence of reporting of KAMs due to being non-listed airlines (e.g., Aer Lingus, Virgin Atlantic, and Aeromexico).

Although the sample refers to the airline industry globally, airlines operating in the US are outside of the scope of this research, because US airlines do not use IFRSs and ISAs. This represents a limitation of this study.

3.2. Research Period

The research period consists of before (2019), during (2020 and 2021), and after the COVID-19 pandemic (2022). Following the prior analysis of the years 2017 and 2018 by Özçelik (2020) and Öztürk (2022), this research extends the existing literature to subsequent years to analyze the airline industry in terms of audit opinion and KAMs, considering the effect of external factors such as the COVID-19 pandemic.

3.3. Research Objective

Considering the research period, the objective of this article is to investigate (a) whether the COVID-19 pandemic had a negative effect on the audit opinions declared in the audit reports of airlines, and (b) whether the COVID-19 pandemic made a difference in the composition of KAMs observed in the airlines’ audit reports.

3.4. Research Methodology

To meet the research objectives, the article primarily pursues a textual analysis, a content analysis, and a frequency distribution, consistent with the methods employed by Özçelik (2020) and Öztürk (2022). The data related to audit opinions and KAMs were manually collected from the audit reports in airlines’ annual financial statements, which are usually directly acquired from their investor relations websites. However, certain procedures were followed in the data collection process related to audit opinions and KAMs.

To collect audit-opinion-related data, an exemplary sentence related to each type of audit opinion (unqualified, adverse, qualified opinion, and disclaimer of opinion) referred to in the audit reports was determined by authors, considering ISA 700 and ISA 705, as follows:

For an unqualified opinion, “The accompanying financial statements give a true and fair view of the financial position of the Company or the Group as of 31 December 20XX […] in accordance with IFRSs”.

For an adverse opinion, “The accompanying financial statements do not give a true and fair view of the financial position of the Company or the Group as of 31 December 20XX […] in accordance with IFRSs” (Fastjet, 2019).

For a qualified opinion, “Except for the effects of the matter described in the Basis for Qualified Opinion section of the report, the accompanying financial statements give a true and fair view of the financial position of the Company or the Group as of 31 December 20XX […] in accordance with IFRSs” (Fastjet, 2020).

For a disclaimer of opinion, “We do not express an opinion on the accompanying financial statements of the Group and of the Company.” (Air Asia X Berhad, 2021).

Considering that airlines’ auditors use similar or equivalent sentences when declaring their audit opinions, the audit opinion paragraphs of each airline’s audit reports were investigated by authors by pursuing a textual analysis in line with exemplary sentences. Following textual analysis, the obtained results were quantified through frequency distribution to observe the composition of audit opinions from 2019 to 2022, and to claim that there was no significant effect of the COVID-19 pandemic on audit opinions. The validity of this claim was also statistically tested via a chi-square test.

To collect data on the composition of KAMs, pages declaring the KAMs in each airline’s audit reports were investigated by authors by pursuing a textual analysis through reading and noting the title of each reported KAM. Following textual analysis, the obtained results were quantified through their frequency distribution in the global and regional context. Following the composition analysis, this article also adopts the threshold approach stated by Öztürk (2022) to classify the main, rare, and very rare KAMs in each year to observe their annual variation. Therefore, it considers the frequency of observation of KAMs both globally and regionally on a five-region basis, which is consistent with Öztürk (2022). The cluster of main KAMs refers to the KAMs that are observed in at least four regions worldwide. The cluster of rare KAMs covers the KAMs that are observed in two or three regions worldwide. The cluster of very rare KAMs includes the KAMs that are observed in only one region worldwide.

To collect data on the subject-specific content analysis of main KAMs, the pages declaring the KAMs in each airline’s audit reports were investigated by authors through a textual analysis, comprising reading and noting the details of each reported KAM, focusing on certain keywords declared in paragraphs describing KAMs and audit procedure disclosures. For instance, useful life, impairment, and residual value refer to the subject-specific content analysis of PPE items. Therefore, first, observations related to each aspect of PPE items were collected and stated as a frequency. Second, the number of total observations were calculated. Third, the number of observations related to each aspect of PPE items was divided by the total number of observations, and finally multiplied by 100 to state the results related to each aspect of PPE items as a percentage of the total observations.

The results obtained were also compared with those in the following studies: Özçelik (2020), Öztürk (2022), Hay et al. (2021), Hategan et al. (2022), Ecim et al. (2023), Kend and Nguyen (2022), Alharasis et al. (2024), Alshdaifat et al. (2025) and Rainsbury et al. (2023).

4. Results

4.1. Audit Opinions in Airline Audit Reports

In the context of the composition of audit opinions in the airline industry, the results from 2019 to 2022 reveal that despite the uncertainty caused by the COVID-19 pandemic, audit opinions in the regional and global context are usually unqualified audit opinions (Figure 1), in line with 2017 and 2018 (Özçelik, 2020; Öztürk, 2022), as expected by Hay et al. (2021).

To verify this fact, a statistical test, namely a chi-square test, was also pursued for unqualified audit opinions. In this context, the following results, as shown in

Table 3. Statistical analysis on unqualified audit opinions.

Statistic	Value
Chi-square (χ2)	0.454
Degrees of freedom (df)	12
p-value	0.9999998

, were obtained.

The chi-square value of 0.454 is extremely small and very close to zero. Correspondingly, the p-value of 0.9999998 is exceptionally high, and very close to the maximum possible p-value of 1. Considering the analysis of variation across five regions and 4 years based on 12 degrees of freedom, both indicators reveal that unqualified audit opinions are extremely stable, regionally and annually. Statistically, there is no significant difference between years or regions regarding the distribution of unqualified audit opinions (Figure 1). This finding indicates that the COVID-19 pandemic did not have a significant effect on audit opinions.

A limited number of audit opinions other than unqualified audit opinions were observed in the airline industry from 2019 to 2022. The first two audit opinions are airline-specific, but the third audit opinion is specific to the COVID-19 pandemic: (a) the auditor of Fastjet declared an adverse opinion for the 2019 financial statements of this airline due to the non-compliance effect to IAS 21, “The Effects of Changes in Foreign Exchange Rates”, but declared qualified opinions due to the survival of non-compliance to IAS 21 in 2020 and 2021 (Fastjet, 2019, 2020, 2021); (b) the auditor of Qatar Airways declared qualified opinions for the airline’s 2020, 2021, and 2022 financial statements due to the misclassification of investment securities as fair value though other comprehensive income which restricts the ability to exercise significant influence in accordance with IAS 28, “Investments in Associates and Joint-Ventures” (Qatar Airways, 2021, 2022, 2023); and (c) the auditor of Air Asia X Berhad declared a disclaimer of opinion in 2021 due to the multiple uncertainties of the COVID-19 pandemic to form an opinion about the airline’s 2021 financial statements. These uncertainties include pandemic recovery; the varying travel and border restrictions implemented by countries; and the significant fall in demand for international air travel, which impacted the airline’s financial position, financial performance, and cash flow (Air Asia X Berhad, 2021).

Within the framework of ISA 200, “Overall Objectives of the Independent Auditor and the Conduct of an Audit in Accordance with ISAs” (FRC, 2022), the audit opinion results reveal that most auditors were able to audit airlines’ financial statements to obtain reasonable assurance about whether the financial statements were free from material misstatement in the periods before, during, and after the COVID-19 pandemic due to fraud or error. Furthermore, they were able to express an audit opinion on whether the financial statements were prepared, in all material respects, in accordance with IFRSs, in the periods before, during, and after the COVID-19 pandemic. In addition, this indicates that they did not face many difficulties or obstacles to declare unqualified audit opinions during the COVID-19 pandemic period (in 2020 and 2021), despite the uncertainty of the pandemic.

4.2. Analysis of Main KAMs in Airline Audit Reports

4.2.1. Main KAMs in Airline Audit Reports in the Pre-COVID-19 Pandemic Period

The KAMs for the year 2019 reflect the accounting period just before the COVID-19 pandemic, like in the cases of 2017 and 2018 in Özçelik’s (2020) study and 2018 in Öztürk’s (2022) study. Within the framework of 126 observations, four main KAMs were observed in the airline industry for the year 2019 (

Table 4. Rankings of main KAMs in the airline industry.

Year	2017 and 2018	2019	2020	2021	2022
Period	Pre-COVID-19	Pre-COVID-19	During COVID-19	During COVID-19	Post-COVID-19
Ranking	Özçelik (2020); Öztürk (2022)
1	Revenue recognition	Revenue recognition	PPE items	Revenue recognition	Revenue recognition
2	Lease accounting	Lease accounting	Revenue recognition	PPE items	PPE items
3	PPE items	PPE items	Lease accounting	Lease accounting	Lease accounting
4	Hedge accounting	Hedge accounting	Impairment of goodwill and intangible assets	Impairment of goodwill and intangible assets	Hedge accounting
5			Hedge accounting	Hedge accounting

): (1) revenue recognition, (2) lease accounting, (3) PPE items, and (4) hedge accounting. They were observed in at least four regions (Figure 2); therefore, they are industry-specific and consist of 71% of observations. These KAMs and their rankings are consistent with the findings of Özçelik (2020) and Öztürk (2022). No change was observed in this context from 2017 to 2018 and from 2018 to 2019. The remaining 29% of KAMs refer to the rare and very rare KAMs observed in the airline industry.

In this context, revenue recognition and lease accounting are especially important main KAMs for the year 2019. The reason that revenue recognition is important is because the 2019 was the second year of the adoption of the new revenue standard IFRS 15, “Revenue from Contracts with Customers ”, following its initial use in 2018 (IASB, 2024a). Therefore, airlines’ auditors strongly audited the accurate adoption and recognition of the new revenue recognition process in 2019 as they did in 2018. Correspondingly, lease accounting is important because 2019 was the first year of the adoption the new lease standard IFRS 16, “Leases” (IASB, 2024b). Because the airline industry as a lessee is a lease-intensive industry (IASB, 2016), auditors attach importance to the audit of accurate recognition of lease transactions at all times, either in line with the former standard IAS 17 in 2017 and 2018 (Özçelik, 2020; Öztürk, 2022) or with the new standard IFRS 16 in 2019.

4.2.2. Main KAMs in Airline Audit Reports During the COVID-19 Pandemic

In contrast to 2017, 2018 and 2019, which marked the period before the COVID-19 pandemic, the year 2020 was the first year of the pandemic. Therefore, the KAMs for the year 2020 reflect the beginning of the accounting period that was impacted by the pandemic. Within the framework of 144 observations, there are five main KAMs in the airline industry for the year 2020 (Table 4): (1) PPE items, (2) revenue recognition, (3) lease accounting, (4) the impairment of goodwill and intangible assets, and (5) hedge accounting. They are observed at least in four regions (Figure 2); therefore, they are industry-specific KAMs and refer to 72% of observations. On the other hand, the remaining 28% of KAMs refer to the rare and very rare KAMs observed in the airline industry.

In this context, the KAMs related to PPE items are especially important for the year 2020, and rank first rather than third in 2020 compared to 2017, 2018, and 2019, due to the introduction of uncertainties into the audit process, e.g., uncertainty related to the determination of impairment, and recoverability of PPE items in accordance with IAS 36, “Impairment of Assets” (IASB, 2024c). In this context, the indication of uncertainty is based on the 2020 audit reports of some airlines from the Asia-Pacific, whose reporting dates are equivalent to 31 December 2019. In addition, revenue recognition is still important for auditors in 2020 for the accurate determination and recognition of revenue under the uncertain conditions of the pandemic.

Following the first year, 2021 was also the second accounting period during the COVID-19 pandemic. In this regard, the KAMs for the year 2021 reflect the accounting period that was impacted by recovery from the pandemic. Within the framework of 130 observations, five main KAMs were observed in the airline industry for the year 2021 (Table 4): (1) revenue recognition, (2) PPE items, (3) lease accounting, (4) impairment of goodwill and intangible assets, and (5) hedge accounting. They are observed at least in four regions (Figure 2); therefore, they are industry-specific KAMs and consist of 72% observations. On the other hand, the remaining 28% of KAMs refer to the rare and very rare KAMs observed in the airline industry.

In this context, revenue recognition and PPE items are still the most significant KAMs; however, the change in the ranking of these KAMs from 2020 to 2021 should not be misunderstood (Figure 2), because a 1% difference exists between the observations of both KAMs. Both KAMs have equal prominence. The uncertainty experienced in revenue recognition, as well as in the recoverability of PPE items, was still significant for auditors in the recovery phase of the COVID-19 pandemic while the audit process was taking place.

4.2.3. Main KAMs in Airline Audit Reports in Post-COVID-19 Pandemic Period

Following the years of the COVID-19 pandemic, the KAMs for the year 2022 reflect the post-pandemic accounting period. Within the framework of 122 observations, four main KAMs are observed in the airline industry for the year 2022 (Table 4): (1) revenue recognition, (2) PPE items, (3) lease accounting, and (4) hedge accounting. They are observed at least in four regions (Figure 2). Therefore, they are industry-specific KAMs and consist of 69 % of observations. Even if their ranking varies, the main KAMs in the post-COVID-19 pandemic period are consistent with those in the pre-COVID-19 period. On the other hand, the remaining 31% of KAMs are rare and very rare KAMs observed in the airline industry.

4.2.4. Overall Analysis of Main KAMs in Airline Audit Reports

Within the framework of these observations, other than the COVID-19 pandemic periods, the results reveal that the main KAMs reported in audit reports of the airlines are usually consistent with those in Özçelik (2020) and Öztürk (2022), and they are in line with those from the years 2017, 2018, and 2019. During the pandemic period, however, there is one additional main KAM in the airline industry, which is the impairment of goodwill and intangible assets (Table 4).

The impairment of goodwill and intangible assets was recognized in accordance with IAS 38, “Intangible Assets” (IASB, 2024d), and was a rarely observed industry-specific KAM in 2017, 2018, and 2019 (observed in three regions), which became a main KAM in 2020 and 2021 (Table 4), being observed in four regions (Figure 2). This is because of the increased uncertainty on how to determine the impairment of assets, which usually include landing rights and time slots (Öztürk, 2022). In the post-COVID-19 pandemic period, this KAM was rarely observed (observed in three regions), once again due to the decreasing effect of uncertainty.

In addition to these findings, hedge accounting has fallen behind its ranking in 2017, 2018, and 2019, and was ranked fifth in 2020 and 2021 (Table 4) during the pandemic period, both because airlines ceased their operations and because the risks that require hedging were minimized. Following the COVID-19 pandemic, in 2022, hedge accounting ranked as the fourth main KAM once again, in line with the period before the COVID-19 period, because airlines’ operations and risks that require hedging fully resumed.

4.3. Subject-Specific Content Analysis of Main KAMs

4.3.1. Revenue Recognition

The subject-specific content analysis of KAMs related to revenue recognition from 2019 to 2022 includes the accurate recording of passenger and cargo revenue, which ranks first (43% of observations on average); the use of complex IT systems to report sales and service revenues accurately, which ranks second (25% of observations on average); the correct recognition of customer loyalty programs, which ranks third (21% of observations on average); and the accurate recognition of breakage revenue (10% of observations on average). These findings are similar to the findings of Öztürk (2022), indicating the auditors’ usual preference to analyze the details of revenue recognition.

4.3.2. Lease Accounting

Compared to the year 2018, from 2019 to 2022, the subject-specific content analysis of KAMs related to lease accounting varies (

Table 5. Changes in the subject-specific composition of KAMs related to lease accounting.

	2018	2019	2020	2021	2022
	Öztürk (2022)
Aircraft maintenance provisions	62%	46%	76%	85%	87%
Aircraft maintenance deposits	10%	2%	5%	5%	-
Lease classification	17%	-	-	-	-
Early adoption of IFRS 16	7%	-	-	-	-
Expected impact of IFRS 16	4%	-	-	-	-
First-time adoption of IFRS 16	-	50%	-	-	-
Compliance with IFRS 16	-	-	19%	10%	9%
Discount rate	-	2%	-	-	-
Accounting for withdrawn funds from letter of credit	-	-	-	-	4%

). The most important subject-specific KAM is the accurate determination and recognition of aircraft maintenance provisions (71% of observations on average), in line with the results for 2018. The analysis of this subject-specific KAM by auditors increased during the pandemic and post-pandemic periods because of increased uncertainty in determining the amount of these provisions. The other important subject-specific KAMs are those that are related to the first-time adoption of, or compliance to, IFRS 16.

4.3.3. PPE Items

In year 2018, the subject-specific content analysis of KAMs related to PPE items indicates a balanced structure, at around 30% of observations (

Table 6. Changes in the subject-specific composition of KAMs related to PPE items.

	2018	2019	2020	2021	2022
	Öztürk (2022)
Residual values	35%	21%	14%	15%	19%
Useful lives	31%	24%	18%	20%	25%
Impairment	35%	55%	67%	66%	56%

). From 2019 to 2021, the analysis of the accurate recognition of impairment and the recoverability of PPE items reveals a significant upward trend, due to the increased uncertainty experienced during the COVID-19 pandemic. In 2022, the analysis of the accurate recognition of impairment and the recoverability of PPE items indicates a slightly downward trend, because the uncertainty of recoverability declined following the pandemic.

4.3.4. Hedge Accounting

The subject-specific content analysis of KAMs related to hedge accounting from 2019 to 2022 includes foreign currency risk, which ranks first (42% of observations on average); fuel price risk, which ranks second (41% of observations on average); and interest rate risk, which ranks third (17% of observations on average). Compared to the findings of Öztürk (2022) from 2018, (a) the questioning of foreign currency risk by auditors increased by 20% on average, particularly during and after the COVID-19 pandemic period; (b) the analysis of interest rate risk declined by 32% on average, particularly in the first year of the COVID-19 pandemic period (2020); and the analysis of fuel price risk by auditors remained unchanged on average.

4.4. Rare KAMs in the Airline Industry

Rare KAMs from 2019 to 2022 refer to the matters declared in

Table 7. Rare KAMs in the airline industry.

2018 Öztürk (2022)	2019	2020	2021	2022
-	Going-concern (COVID-19-specific)	Going-concern (COVID-19-specific)	Going-concern (COVID-19-specific)	-
Provisions for taxation, litigation, and claims	Provision for litigation, taxation, and claims	-	Provision for litigation, taxation, and claims	-
Deferred tax assets and liabilities	Deferred tax assets and liabilities	Deferred tax assets and liabilities	Deferred tax assets and liabilities	Deferred tax assets and liabilities
Pension plans	Pension plans	Pension plans	-	Pension plans
Impairment of goodwill and intangible assets	Impairment of goodwill and intangible assets	-	-	Impairment of goodwill and intangible assets
Carrying value of inventory	Carrying value of inventory	Carrying value of inventory	Carrying value of inventory	-
Defined benefit plan obligations	-	-	-	-
First adoption of IFRS 9	-	-	Impairment of long-term investment	-
New aircraft purchases	-	-	-	Going-concern (airline-specific)

, and are observed in two or three regions worldwide (Figure 3 and Figure 4). Other than the industry-specific KAMs observed in 2019 and 2021 (e.g., the provision for litigation, taxation, and claims) and in 2019 and 2022 (e.g., the impairment of goodwill and intangible assets), as well as KAMs specific to the COVID-19 pandemic observed in 2019, 2020 and 2021 (e.g., going-concern specific to the COVID-19 pandemic) (Figure 4), all other KAMs are airline-specific from 2019 to 2022 (Table 7). Except for going-concern specific to the COVID-19 pandemic, these rare KAMs are mostly similar to the matters declared by Öztürk (2022) because they are observed in the airline industry, but not as much as the main KAMs regionally.

Other than the going-concern specific to the COVID-19 pandemic, rare KAMs are mostly investigated by auditors operating in Europe and thereafter in Asia-Pacific (Figure 3). The motivation of auditors in the Middle East and Africa is limited to the analysis of the carrying value of the inventory. While the auditors in China and Northern Asia mostly focus on (1) the impairment of goodwill and intangible assets and (2) deferred tax assets and liabilities, the auditors in the Americas mostly concentrate on (1) pension plans and (2) going-concern specific to an airline. Nevertheless, the classification of these KAMs is subject to change depending on the number of regions whose particular KAM is observed annually (Figure 3). Therefore, a rare KAM may usually be a rare KAM (e.g., deferred tax assets and liabilities); however, it may also turn out to be a main KAM (e.g., impairment of assets and intangible assets), or may switch from a rare KAM to a very rare KAM (e.g., provision for litigation, taxation and claims, carrying value of inventory, impairment of long-term investment).

Considering the composition of rare KAMs, on the other hand, it should be noted that the COVID-19 pandemic period creates a new, rare KAM; namely, going-concern specific to the COVID-19 pandemic, which is created by the financial effect of the pandemic. In 2019, it is observed in two regions (Europe and Asia-Pacific) in the airline industry (Figure 4). However, it is observed in three regions in 2020 (Europe, Middle East and Africa, and Asia-Pacific) and in 2021 (Americas, Europe, and Asia-Pacific) in the airline industry due to the increasing financial effects of the pandemic, and auditors’ doubts about the financial health and survival of airlines due to the pandemic. Regionally, the questioning of going-concern specific to the COVID-19 pandemic is mostly pursued by auditors operating in Europe from 2019 to 2022 (Figure 4). They analyzed the precautions taken by the airline management to make sure that airlines met the going-concern assumption of accounting. Following the recovery phase of the pandemic in 2021, going-concern specific to the COVID-19 pandemic turned out to be a very rare KAM in 2022 due to the pandemic’s decreasing financial effect on the going-concern assumption of accounting.

4.5. Very Rare KAMs in the Airline Industry

Very rare KAMs from 2019 to 2022 refer to the KAMs presented in

Table 8. Very rare KAMs in the airline industry.

2018 Öztürk (2022)	2019	2020	2021	2022
-	Impact of the COVID-19 pandemic (in general)	Impact of the COVID-19 pandemic (in general)	Impact of the COVID-19 pandemic (in general)	-
-	Pension plans	-	-	-
Acquisition accounting	Acquisition accounting	-	-	-
-	Recapitalization	-	-	-
-	French tax investigation	French tax investigation	-	-
-	Classification of investments	-	-	-
-	Classification of exceptional and other items	Classification of exceptional and other items	-	-
-	Cyberattacks and cybersecurity	-	-	Cyberattacks and cybersecurity
Convertible bond	Convertible bonds	Convertible notes	-	-
-	Restructuring provision	Restructuring provision	-	-
-	Government grants	Government grants	-	-
Going-concern	Going-concern (airline-specific)	Going-concern (airline-specific)	Going-concern (airline-specific)	-
Change in accounting policy	-	Defined employee benefit plans	-	-
Accuracy of opening balances	-	Accounting for ST working allowances	-	-
-	-	Valuation of investment properties	Valuation of investment properties	Valuation of investment properties
-	-	Stock warrant obligations	Stock warrant obligations	Stock warrant obligations
EU 261 provision	-	Risk of material misstatement	-	-
Disposal of trade operations	-	Assets, liabilities held for sale	-	-
Functional currency	-	-	SAS Forward Business Transformation Plan	SAS Forward Business Transformation Plan
Accounting for one-off items	-	-	Non-recurring expenses	-
Carrying value of receivables	-	-	-	Restructuring plan on going-concern
Loan classification	-	-	-	Loans and receivables due (intercompany)
Asset retirement obligation	-	-	-	New financial reporting system
Accounting for cash-generating unit	-	-	-	Accounting for joint-ventures
-	-	Provision for litigation, taxation, and claims	-	Provision for litigation, taxation, and claims
-	-	-	-	Carrying value of inventory
-	-	-	-	Going-concern (recovery from the COVID-19 pandemic and the war in Ukraine)
				Impairment of LT investment

. They are observed in one region depending on annual observations. Other than the industry-specific KAMs observed in 2020 and 2022 (e.g., the provision for litigation, taxation, and claims) and COVID-19-specific KAMs (e.g., going-concern specific to COVID-19, impact of the COVID-19 pandemic (in general)), all other very rare KAMs are airline-specific from 2019 to 2022 (Table 8). They are less similar to the ones declared by Öztürk (2022), and they are diverse.

Some of very rare KAMs that do not change their clusters depending on annual observations are mostly investigated by auditors operating in Europe. While the motivation of auditors in the Middle East and Africa is the analysis of the valuation of investment properties, the focus of auditors in China and Northern Asia is government grants. In addition, the focus of auditors from the Americas is on (1) stock warrant obligations, (2) convertible bonds, and (3) new financial reporting systems.

Nevertheless, the classification of some very rare KAMs is subject to change, depending on the number of regions in which a particular KAM is observed annually (Figure 5). Therefore, a very rare KAM may usually be a very rare KAM (e.g., acquisition accounting, recapitalization, French tax investigation, classification of investments, classification of exceptional and other items, convertible bonds, convertible notes, restructuring provisions, government grants, defined employee benefit plans, accounting for ST working allowances, valuation of investment properties, risk of material misstatement, assets and liabilities held for sale, SAS forward business transformation plan, non-recurring expenses, loans and receivables due (intercompany), restructuring plan on going-concerns, new financial reporting systems, and accounting for joint-ventures). However, it may also turn out to be a rare KAM (e.g., pension plans), or may switch from a very rare to a rare KAM (e.g., provision for litigation, taxation and claims, going-concern specific to airlines) (Figure 5).

In addition, the impact of the COVID-19 pandemic (in general) on airlines remained a very rare KAM; it was only observed in Europe in 2019, 2020, and 2021.

5. Discussion and Conclusions

This article focuses on audit opinions and KAMs in the context of airlines adopting IFRSs and ISAs from 2019 to 2022 within the framework of the periods before, during, and after the COVID-19 pandemic.

In terms of audit opinions, the results reveal that the audit reports of airlines adopting IFRSs and ISAs usually declared unqualified audit opinions from 2019 to 2022. This finding is consistent with the prior research of Özçelik (2020) and Öztürk (2022), as well as with the hypothesis of Hay et al. (2021). In this regard, it should be noted that despite the uncertainty created by the pandemic, except for the case of one airline company whose audit report declared a disclaimer of opinion, the COVID-19 pandemic did not have a significant effect on audit opinions. It appears that auditors did not experience any severe difficulties in precluding themselves from meeting necessary audit requirements (e.g., reasonable assurance requirements) to prepare airline audit reports. However, this may not be the case for airlines operating in the US. Therefore, further research is necessary to investigate the effect of the COVID-19 pandemic on audit opinions related to airlines operating in the US.

In terms of the composition of KAMs, this research reveals that revenue recognition, lease accounting, PPE items, and hedge accounting are the main KAMs that are usually declared in the airline audit reports, which is in line with the findings of Özçelik (2020) and Öztürk (2022), and in parallel to the key accounting topics observed in the airline industry (Lavi, 2016). However, it should be noted that the COVID-19 pandemic affected the composition of KAMs due to the increased uncertainty of the pandemic by adding the impairment of goodwill and intangible assets into the composition of main KAMs, and going-concern specific to the COVID-19 pandemic into the composition of rare KAMs in 2020 and 2021. While the overall composition of main KAMs is usually consistent with the KAM topics stated by Hategan et al. (2022), Ecim et al. (2023), Kend and Nguyen (2022), Alharasis et al. (2024), Alshdaifat et al. (2025), and the standards declared by Rainsbury et al. (2023) (e.g., revenue recognition, PPE items, impairment of goodwill and intangible assets), it deviates from them regarding lease accounting and hedge accounting, which are the main KAMs specifically observed in the airline industry. In addition, the details of the main KAMs also reflect the effect of the COVID-19 pandemic. The increase in the number of main KAMs may also be the case for airlines operating in the US in terms of the composition of critical audit matters (CAMs) due to uncertainty related to the pandemic. Therefore, further research is necessary to investigate the effect of the COVID-19 pandemic on the airlines’ CAMs operating in the US.

Considering the KAMs related to the COVID-19 pandemic, it should be noted that the impact of the COVID-19 pandemic (in general) disappeared in 2022. However, going-concern specific to the COVID-19 pandemic, which includes recovery from the COVID-19 pandemic and the war in Ukraine, is only observed in Europe in 2022, because even though the airline industry had recovered from the COVID-19 pandemic, the war in Ukraine was still ongoing. The KAM analyzing going-concern is expected to remain due to the war in Ukraine.

Other than the effect of the COVID-19 pandemic on audit opinion and KAMs, further research regarding the airline industry is necessary to analyze whether the Russia–Ukraine and Israel–Palestine conflicts, which have had negative effects on flight operations, have had any effect on the audit opinions and KAMs observed in the airline industry.