Risk and preventing of COVID-19 grounded aircraft-value, risks and resilience: an ongoing debate

ABSTRACT Design/methodology/approach This paper used pervious related to aviation literatures to summarise and viewpoint the current aviation environment and conduct the risks, value, and resilience of grounded aircraft-value in the post-pandemic era. Purpose Throughout 2020 to date, this major event, known as SARS CoV-2, has had a decisive impact on global air transport. Since the outbreak began, passenger travel has declined due to infection risks and new laws and travel restrictions. Dependent Surveillance-Despite the recent recovery in demand from the airline industry, risks posed by new models remain a concern for many airlines. From the data of Broadcasting (ADS-B) is helpful for preliminary observation and judgment of the value level of a certain type of aircraft. Findings This paper not only focuses on the aviation environment, but discusses aviation highlights such as international perspectives, domestic (i.e. Taiwan) perspectives, and several issues between industry and academic perspectives. Research limitations/implications The next phase of research needed in this area is a closer assessment of the value of aircraft in the development of global networks, which could have important policy implications for aircraft manufacturers and the aviation industry. Originality/value This paper provides a contemplative perspective about the aviation industry.


Introduction
The global air transport market in the past two decades, whether it is the 9/11 incident, the Gulf War or the financial crisis, its impact on the aviation industry is far less than the impact of the new global epidemic (i.e. .Throughout the year 2020, COVID-19 has evolved into a full-blown pandemic, posing a global risk to human health and the global economy.The disease was first detected in China in December 2019.By 5 October 2020, the World Health Organisation (WHO) found Delta as a SARS-Cov-2 Variants (HER, 2021).The long-term effects of COVID-19 remains unpredictable, especially with the discovery of Omicron in South Africa in November 2021.Of all industries, aviation is probably one of them hardest hit (Suau-Sanchez et al., 2020).Dependent Surveillance-Broadcasting (ADS-B) is helpful for preliminary observation and judgment of the value level of a certain type of aircraft.According these recently three years' statistic (see Figure 1), the pandemic-related disruptions caused uncountable flight cancellations (Dray & Schäfer, 2021).Furthermore, during the epidemic, aircraft utilisation has become an important factor affecting the value of aircraft.
Since the outbreak of the epidemic, due to factors such as the sharp drop in the willingness of travellers to travel, the tightening of border controls by countries, and the closure of many airlines, the aircraft utilisation rate has dropped significantly (Chaisse & Banik, 2020).After an 18-month slump, finally, European carriers had started to see an uptick in international air traffic in the summer of 2021.Part of the increase in air traffic is due to higher vaccination rates and easing of travel restrictions.Travel demand has plummeted during the pandemic, forcing many flight cancellations and driving employees to voluntarily leave or take furloughs to reduce labour costs.Today, with the recovery of tourism demand, in addition to airlines, retail, catering and hospitality industries have also begun to actively recruit employees.American Airlines, for example, hired more than 16,000 workers in 2021 and announced to hire 18,000 workers in 2022 as it prepares for a resurgence in tourism.The stock market is also motivated by BNT companies, and most tourism industries are profitable, such as Hyatt Regency US, Marriott Hotels US, and Hilton Worldwide.
The emergence of Omicron, however, during the main holiday period in late 2021, which spreads significantly faster than Delta (see Table 1), could alter the evolution of the outbreak.Overall demand is recovering, thanks to higher ticket sales, but the shift is still cause for concern for many airlines.Today, a highly contagious variant of the virus has been identified in at least 100 countries, forcing tighter restrictions.In addition, American Airlines announced the suspension of new international routes before the epidemic, and Boeing (BA-US) has repeatedly delayed the delivery of the 787 Dreamliner.It can be seen that in the second year after the outbreak of the new crown epidemic, the value of the aircraft has changed rapidly.In addition, navigating the new testing rules has proven to be a huge challenge as more details about the new variant emerge.

Materials and methods
This study adopted a systematic literature review (SLR) approach as it ensures the most efficient and high-quality approach to exploring and evaluating a large body of literature.From the research background, this SLR ground study is limited to the information available on the aircraft and the COVID 19-WOS database, and applied to literature mining (see Figure 3).When looking for data for this study, the researchers set some criteria to select more relevant papers in the field.In other words, it is a reliable and widely accepted database containing various peer-reviewed journals in the fields of business, economics and management (Anees- Ur-Rehman et al., 2016;Foroudi et al., 2021).Following the criteria of Tranfield et al. (2003) and some oft-cited review publications, the systematic review process in management research can be carried out in three phases: 1) planning the review; 2) conducting the review; 3) reporting.Reviews include review papers and articles.Each identified classification was then carefully screened to identify relevant records, with only 133 studies ultimately selected for inclusion in the comprehensive review.Figure 2 details the overall process of the statement for selection and rejection of current studies.

Descriptive analysis
The outbreak has affected current industry-academia trends, including international and domestic aviation markets.Many of the related articles focus on medical issues, some on discussions of capabilities and operational analysis (see Figure 4 and Figure 5).Medical issues were not the focus of this study as the consideration is that the longer an aircraft is stored, the more expensive it will be to restore it to service in the aviation industry.However, despite the negative impact in 2020, transfers of aircraft between operators will still occur, albeit at much lower rental levels and even on an hourly basis.There is still a room to consider and investigate on the value of aircraft in the post-epidemic era.Operators will also experience changes in longer service recovery times due to improved communications, reduced initial economic activity and constrained corporate travel budgets due to the need for long-distance travel.Under such market conditions, new   aircraft are often used as replacements rather than growth capabilities, forcing older aircraft to retire early.Some new aircraft are delivered only for long-term storage.
The severe crisis engulfing the aviation industry will have profound implications for aviation finance in an increasingly competitive and regulated market, as the pandemic has hit the value of Airbus and Boeing's most popular mid-life planes.As the market improves over the next few years, the value of narrow-body aircraft is likely to exceed pre-COVID-19 forecasts through 2025 due to lower production rates and increased  retirements of older aircraft.Even if the plane's market value is no longer inflated, it's important for investors to stress-test new deals before proceeding.If the economic recovery is slower than expected, aircraft values could fall further.On the other hand, since the onset of the pandemic, several articles have been published in prestigious journals, such as Elsevier, Springer Nature, and Wiley, discussing the industry's difficulties and impacts that have followed.In particular, most of the research areas focus on public health and environmental issues and research (n = 101), which is sufficient to demonstrate that policy can influence the survival mode of the industry.Likewise, understanding how to improve the business model of aviation requires precisely the value of the future aviation industry -aircraft (n = 26), and future research should also focus on this.

International view
There are various factors, such as supply and demand, oil price and capital, and technological updates, jointly determine the value of the aircraft market (e.g.Bozkaya et al., 2022;Gansterer et al., 2021;Nguyen, 2020;Ripoll-Zarraga & Lozano, 2020).For example, Boeing delivered a total of 302 aircraft in the first 11 months of 2021, more than double the number in the same period last year.Airbus also nearly tripled its order book over the same period as Indigo Partners ordered 255 A321 neos.However, in the short term, the volatility of the epidemic has had a negative impact on the market demand and utilisation of older models, which in turn has weakened the possibility of a substantial recovery in the market value of these models.Aviation Industry should constantly explore new trends to cover the market value of mainstream commercial aircraft.Airbus originally had more than 4,000 orders for the A320neo, but then the trend turned to larger-body Airbus.Airbus and partners (i.e.Spirit, GKN, Daher) also set up a Wing of Tomorrow project to develop composite OOA technology for the manufacture of next-generation single-aisle airliner wings.As a result, the A321neo was developed to redesign the entrance to accommodate more passengers.Furthermore, the A32 LR will be followed by the A321XLR which is an extra-long range (see Figure 2).The Cirium Aviation Insights report (2022) expects global domestic passenger traffic to return to pre-pandemic levels in terms of passenger numbers by the end of 2022.In same time, international passenger traffic could reach 23% of 2019 levels.The capacity in 2022, thus, is expected to increase by 47% compared to last year in terms of seats flown.From a long-term perspective, the continuous entry of a new generation of commercial aircraft will re-determine the value centre of the aircraft (Hamdan et al., 2022).

Domestic view
The commercial aircraft market is relatively sluggish as the epidemic.The aviation industry, as shipping has plummeted by at least 80%, has relied on a lot of debt to survive the recession.The revenue of the two major civil aviation industries in Taiwan has returned to pre-pandemic levels in 2021.The November revenue of China Airlines was the highest point since July 2019, while EVA Air's annual growth rate in November 2021 was 57.1%.Only by having maintenance skills to master the flight safety (Ellis & Jimenez, 2022).Therefore, EVA Aerospace invested heavily in the maintenance centre, and introduced General Electric Company's (GE) funds to invest 20% of the shares, so that EVA Aerospace was designated as the designated maintenance plant of GE Asia (Merkert, 2023).In addition to the two major aerospace industries in Taiwan were deeply affected and began to shift their business scope to the military aircraft market.Besides the layout in the aerospace field, Aerospace Industrial Development Corporation (AIDC) has also begun to extend the business of electric vehicles and energy storage systems (Tsui et al., 2022).Due to the negative annual growth rate in 2021, AirAsia has expanded its military helicopter maintenance business and extended its tentacles to leasing companies to discuss the parking and return inspection business.000000

Aircraft boarding
From an air transportation system perspective, a flight can be viewed as a gate-to-gate or air-to-air process.On-time operations depend on the performance of all involved parties (air navigation service provider (ANSPs), network management, airports, airlines).To achieve the target value of on-time performance, airlines implement time buffers to compensate for deviations at the operational level (Fota et al., 2014).As an exception, the boarding process depends on the passenger's experience and willingness or ability to follow recommended procedures (e.g.lateness, no-show, number of hand luggage, identity passenger).The concept of these aircraft boarding has been a major focus in the field for the past 10 years.Specifically, seat loads and passenger behaviours during aircraft boarding are calculated and checked to establish dynamically optimised aircraft boarding strategies (e.g.Gwynne et al., 2018;Schultz, 2017;Tang et al., 2018).Notably, the COVID-19 outbreak has impacted air travel safety requirements.Recent research still focuses on the issue of aircraft boarding (e.g.Scardaoni et al., 2021;Sun et al., 2021;Tabares, 2021, see Table 2).
Changes in aircraft fuselage and cabin layout are expected to enhance the market potential (Scardaoni et al., 2021).More specifically, single-aisle aircraft will become a post-pandemic trend, helping to increase passenger demand while helping aviation revenues return to pre-pandemic levels as soon as possible (de Oliveira et al., 2021; Tanida & Niari, 2021).It can be found that industry and academia are simultaneously analysing and discussing this trend to ensure that the value of aircraft can stabilise in the post-pandemic era.Therefore, the performance of affordable passenger and cargo services may be seen as a new opportunity for the aviation industry (Sun et al., 2021).

Passenger demand
Against a backdrop of tight liquidity, thin margins and high burn rates, the performance of the aviation industry depends on macro predictability, micro uncertainty and macro environmental factors (Merkert & Swidan, 2019;Mhlanga, 2019;Stamolampros & Korfiatis, 2019), resulting to range from severe losses to aviation bankruptcy.Aviation is the hardest-hit sector, as the pandemic has proven to be highly disruptive (Laing, 2020;Wren-Lewis, 2020), with a projected loss of $84.3 billion in 2020 (Sing, 2020).Depending on the intensity and duration of the outbreak, containment measures, and the economic and psychological impact, worldwide seat availability could drop by 33% to 60%, with passenger traffic falling from 1.878 billion to 3.227 billion (Hasegawa, 2022), and the same year total loss of operating income was approximately $2.44 billion to $420 million.
The aviation industry expects a severe drop in its passenger traffic due to travel and destination restrictions, phobias, declining tourism and reduced business activity (Thams et al., 2020).Part of the reason customers want to book closer to departure is that different countries are imposing travel restrictions more frequently than before COVID-19.Additionally, airline passengers booking and traveling during the COVID-19 recovery need to be able to easily change their flight and travel plans, given changing travel restrictions and the emergence of new COVID-19 hotspots.Some of these changes, particularly when passengers purchase tickets and how often they change, are especially challenging for airlines as they affect multiple functional areas.Given that COVID-19 May have irreversibly changed consumer behaviour, the importance of understanding how airline passenger demand is changing, many innovations are taking place in the industry in anticipating demand (Hanson et al., 2022).Research is needed to help identify new business models and new data sources that can be used to forecast airline demand, and which forecasting methods to transition to a more sustainable form over time that balances customer satisfaction and revenue maximisation to the best price point (Sharma et al., 2021;Zhao et al., 2021).Taken together, COVID-19 has caused fundamental changes in airline passenger demand, and many of these changes are expected to remain in place after the on-going variant pandemic (see Table 3).

Operation: lessons from COVID-19
Airline business models have evolved over time, with one major change resulting from market liberalisation that began in the United States in 1978 and ultimately created opportunities for low-cost models (Chaudhuri et al., 2021;Kabadurmus & Erdogan, 2020).In addition to the overall airline schedule planning problem, which is difficult to compute considering both FSC and LCC, it is usually divided into smaller sub-problems (Papadakos, 2009), including schedule design (Lohatepanont & Barnhart, 2004), fleet Allocation (Sherali et al., 2006), aircraft routing (Gopalan & Talluri, 1998) and crew scheduling (Hoffman & Padberg, 1993).Therefore, in recent years, research has increasingly considered integrating subproblems into larger parts for optimisation, such as fleet allocation/aircraft routing (Barnhart et al., 1998;Liang & Chaovalitwongse, 2012) and timetable design/aircraft routing (Faust et al., 2017.Airlines face numerous challenges in their efforts to ensure the high efficiency of their operations (Deveci & Demirel, 2018).Problems in airline operations are complex, and it is difficult for managers or researchers to model and solve them in a reasonable time, such as manpower planning.In the last decade, many studies have been published to address manpower planning issues, such as class scheduling for pilot training (Qi et al., 2004), health workforce planning (Batenburg, 2015;Willis et al., 2018), domestic freight forwarding (Batenburg, 2015;Dewi & Septiana, 2015;Willis et al., 2018), call centre workforce planning (Excoffier et al., 2016), rotating workforce schedules (Kletzander et al., 2021), and airport check-in counter planning (Wibowo & Fadilah, 2018).To meet this demand, airlines must not only consider manpower planning, but also better prepare for a pandemic of this magnitude for the first time in our life (see Table 5).However, the strategies employed so far have been insufficient to deal with the epidemic situation, as there have been many reports of people facing serious difficulties of various natures.More recently, the

Global
The distance between origin and destination has a negative effect on demand stimulation, so smaller airports generally have higher passenger incentives as nonstop services are introduced.

Leandro et al. (2021) Global
The synergy of air and sea connectivity can meet the demands of different areas, especially in the coming years.Zhao et al. (2021) Global It states a dynamic pricing mechanism of ancillary services based on passenger choice behaviours, reaching the best price point of balancing customer satisfaction and revenue maximisation.Dixit and Jakhar (2021) Global It noted the most literature on "airports" were related to civil and construction and airport capacity without the involvement of practitioners, airline-airport industry partners and/or policy makers.
authors in Huang et al. (2021) and Pushparaj et al. (2021) reviewed the decision-making challenges in strengthening airport weaknesses and providing employees with reliable flight plans.We need a more detailed and robust action plan that considers the multiple criteria that will be impacted during the pandemic.

Research gaps and directions for the research agenda after COVID-19
Our systematic review shows that there is a room to update the research agenda in the aviation industry and environment in the future.Based on the results of this present review, and by considering the challenges to COVID-19, this section identifies and summarises research gaps and proposes research avenues to fill them are proposed.On the other hand, the restrictions of COVID-19 have brought new challenges to the practice and development of various aviation industries in the future.The requirements of the research path identified in this paper are: (1) public health; (2) environmental issues; (3) business models; and (4) aircraft storage.

Brazil
The spread of passenger confidence or government restrictions directly affected by the COVID-19 outbreak has directly affected airline operations and demand worldwide.Choi (2021) Global In the wake of Covid-19, increased dwell time has a more significant effect on increasing spending by existing buyers than creating new buyers.Dixit and Jakhar (2021) Global It noted the most literature on "airports" were related to civil and construction and airport capacity without the involvement of practitioners, airline-airport industry partners and/or policy makers.Defossez (2021) Global An exhaustive list of special circumstances, such as COVID 19, seems appropriate and helpful.Leandro et al. (2021) Global Explore demand forecasting models and optimisation models, reduce existing flight scheduling and fleet planning costs by 4% to 20%, and plan PSO aviation networks.Kim and Sohn (2022) South Korea South Korean airlines' response to the COVID-19 crisis on retrenchment, perseverance, innovation and exit.Jorge et al. (2021) Brazil The busiest airports that handle slot allocation with optimized decision support tools are PSAM-based.
The pandemic has since transformed research, focusing on the impact of the crisis in the early stages of the pandemic on airline business models and strategies.Some authors point to the permanent effects of the COVID-19 crisis in the long run, and whether the crisis presents an opportunity to transform the aviation industry to address needs related to societal challenges (see Table 4).In this regard, most of the literature on "airports" is related to civil and construction and airport capacity without the involvement of practitioners, airline-airport industry partners and/or policymakers (Dixit & Jakhar, 2021).Research in this area should address the crises of austerity, persistence, innovation, and exit (Kim & Sohn, 2022).

Global
It has developed a multi-time-scale airport GH management structure with an online solution that can be easily extended to all GSE fleet types performing aircraft GH at the airport.

Shin et al. (2022) Global
It noted that emotional support significantly reduced the positive relationship between supervisor incivility and job insecurity.Huang et al. (2021)

Global
The four dimensions of this paper is helpful for managers to strengthen the weaknesses of the airport.Pushparaj et al. (2021) Global Brain imaging validation using functional magnetic resonance imaging (fMRI) data to construct and generate reliable flight plans with visible waypoints and airports.

Sustainability action plan considering COVID-19 implications
In the past, brands and businesses spent a lot of money on marketing, travel, etc., and mostly focused only on first-class customers.An appropriate balance needs to be struck between achieving post-pandemic operational normality and promoting air transport growth and development.Still, it's worth noting that no matter how good a business model is, its effectiveness will be compromised if it is not followed carefully.
A key challenge for industry and businesses is that environmental issues are likely to become more prominent, absorbing the environmental agenda and intense pressure from stakeholders with post-pandemic interests and conflicts (Singh et al., 2023).In other words, COVID-19 reminds us of the importance of proactively responding to looming crises and the need to act to avoid firefighting (Vetter, 2020).The broader environment focuses on energy scarcity and carbon emissions, as new aircraft manufacturing, fuel requirements for flight operations and the resulting carbon emissions are considered by all airline groups to be the most significant impact of flying (Thummala & Hiremath, 2022).Compliance requirements and codes of conduct regarding environmental issues generally extend to suppliers, which are regularly assessed.

Making the more opportunities
The International Air Transport Association (IATA), aircraft manufacturers, industry stakeholders, and even the World Health Organization (WHO) are working to develop guidance on non-pharmaceutical interventions to limit the spread of infectious diseases on board aircraft.However, there are no medical personnel on board and cabin crew are expected to be 'first responders', raising questions about the extent to which infectious diseases will be covered in airlines' future internal training courses.Employee perceptions are another motivating factor (see, for example, Ng et al., 2023;Sun et al., 2021;Yiu et al., 2022).The COVID-19 pandemic has added a whole new dimension to flight education and training, highlighting the importance of understanding flight attendants' perspectives on training.

In-depth analysis of the COVID-19 long-term effects
Closing part of the airport's aircraft storage means creating new taxiway layouts.The reason aircraft storage is so labor-intensive is that extensive measures are required to anticipate and prevent damage from various hazards.It should be noted that some routine aircraft storage tasks include closing all openings to protect wildlife and debris, sealing engines, lubricating flight controls and landing gear, installing sunshades, and taking steps to minimize cabin humidity.Additionally, aircraft energy storage is a common response to low demand, highlighting the extent of the challenge that designers of zero-emission aircraft face in finding alternative aviation energy storage solutions compared to other industries (Mai, 2021).In other words, aircraft designs must try to implement weight-saving technologies, lower payload ratios and green energy storage, or simply build bigger planes for the same number of passengers (Santos & Delina, 2021).

Conclusion
In sum, from the literature the major debates and discussions revolved around the antecedents and consequences of the epidemic, and almost all governments face similar political regulations.However, there are lack of validation with the involvement of practitioners, industry partners and/or policy makers.Secondly, in the industry side, it more considers operation management in the coming future.For the literature, furthermore, most are the concept papers, involving aircraft boarding, passenger demand, operation issues and manpower.Nowadays, the overall business environment is relatively unstable, affected by factors such as the epidemic and war, the aviation industry has continuously revised the value of aircraft to fit market demand.On the other hand, academia has not kept pace with changes in industry and the overall environment, and future research needs to take this research gap into account.The aviation industry knows that aircraft should lose weight, which will help reduce fuel costs.This timing is an important inflection point that requires a rethinking of the value of aircraft, especially the various types of future aircraft produced in response to current events, such as windowless, electric and aerospace planes.Aircraft leasing will, thus, continue to be a major part of the aviation industry, and the role of lessors will grow as they continue taking on more aircraft through sale-and-leaseback deals with airlines.But in the near term, lessors will face heavy turbulence and a bumpy road before the industry begins to recover.The rapid transformation of the virus, the Russian-Ukrainian war, etc. may continue to cause turmoil in the aviation industry, but issues that are more important than operations must be considered.The next-step research should give a closer look at the evaluation of aircraft value to establish the link between worldwide network development, which can generate important policy implications for both aircraft manufactories and airline industry.
A prolonged lockdown will hit vulnerable airlines hard with thin profits, liquidity crisis, high fixed costs and heavy debt.Zero revenue has been draining airlines' cash reserves, leaving the industry facing a severe recession in the future.This paper contributes to a deeper understanding of the aircraft industry.The purpose of this descriptive study is not to extrapolate any meaning in the report or make any statistical inferences, but rather to measure application in a broad context of the global passenger aircraft industry.Regarding the implications for scholars, this study contributes to the ongoing discussion on the impact of pandemic on potential crises and issues in industry supply chains and business activities.Specifically, this article explores the challenges and opportunities for stabilizing operations in an adverse aviation business environment created by pandemic, as opposed to a benign environment for policy initiation and adoption.Given that the impact of pandemic eventually subsides, airlines are likely to return to growth, as are noise and air emissions.Airlines therefore need to be helped to survive in the short term without abandoning their commitment to decarbonization and a sustainable global economy.In other words, businesses also need flexibility to improve their chances of survival.In this novel coronavirus environment, global airlines can no longer compete solely on their environmental commitments but will need to take additional safety measures to protect the health of their passengers.This shift from short-term to long-term, and from conservative to data-informed planning and action is possible through greater collaboration between the public and private sectors, whether in the development of new aircraft designs or aircraft storage.
This study has several limitations that future research could address.The sample is limited to relevant literature from 2020-2022.Moreover, it is limited to English literature.It is actually difficult to understand the internal material conditions of other countries with different language families.Finally, this study is limited to the business management literature and may also exclude some important aviation research results.Based on the above limitations, we make the following recommendations for future research.Therefore, longitudinal studies can explore changing reporting trends.Such studies can also statistically verify regional differences.In turn, causal studies could reveal the determinants of the use of various reporting tools, which is beyond the scope of this study.The results of direct research can also be considered to discuss needs and difficulties between industries.People from different nationalities or working for other airlines may have different perspectives on their company's operations.

Figure 1 .
Figure 1.All commercial flights from Jan 2019 to Jul 2022.* Commercial flights: commercial passenger +cargo+charter+some business jet flights.

Figure 3 .
Figure 3.The process of inclusion and exclusion criteria.

Table 2 .
The key article about aircraft boarding during 2021-2022.
Scardaoni et al. (2021)y (i.e.infectious detection means) and the build of appropriate industry standards and State regulations will be the enabler to trigger the responsibility discussion about the Pandemic-free travel.Scardaoni et al. (2021)Global It estimated and expected the economic performance of the TAT of an aircraft such times due to fuselage and cabin layout variations and, thereby, improved marketability potential.

Table 3 .
The key article about passenger demand during 2021-2022.

Table 4 .
The key article about aircraft operation during 2021-2022.

Table 5 .
The key article about manpower during 2021-2022.