Cabin crew health and fitness-to-fly: Opportunities for re-evaluation amid COVID-19

Abstract

Aircrew fitness-to-fly is among the elements that make aviation the safest form of long-distance transport. The health of cabin crew is a crucial determinant in carrying out safety-related duties. ‘Fitness-to-fly’ is associated with defined workplace conditions, for which airlines have a legal duty to ensure fitness for employment. We explored the literature on fitness-to-fly to obtain a pragmatic assessment of the challenges for aeromedical examinations. Regulations promulgated by aviation regulatory authorities and airline-internal policies have similar status and meaning, yet there is no harmonised approach internationally, and an inability to conform periodic medical assessments to actual operational fitness. The COVID-19 pandemic has highlighted the need to better understand fitness-to-fly criteria. Fitness-to-fly measures are mainly based on self-reported data and there is a need for a ‘safety’ factor for self-reports. Aeromedical evaluations should evolve from meeting medical standards to include pandemics as an element of the overall risk of aircraft operations. Re-evaluating criteria for fitness-to-fly assessment will further the goal of linking research to the actual needs of public health decisionmakers. If airlines are to resume operations at pre-pandemic levels, they must demonstrate to the public and public health agencies that fitness-to-fly assessment is appropriate and effective.

1. Introduction

Cabin crew play a key role in maintaining passenger and operational safety in commercial aviation. Prior to the COVID-19 pandemic, cabin crew were a fast-growing occupation, with demand for new recruits expected to rise between 2018 and 2038 to over 300.000 crewmembers in regions such as the Asia Pacific [1]. Similar to the activities involved in the work of police officers, paramedics, and fire fighters [2], there are public health issues associated with the activities of cabin crew. Although good health is a crucial determinant in carrying out safety-related duties, the critical public safety role of cabin crew and the concomitant demands for good health often go unrecognised [3]. Through identifying the effective skills and knowledge required to ensure cabin safety, fitness-to-fly standards aim to contribute to continuous safe flight operations, and to protect the health and safety of passengers.

Cabin crew work in a high-risk environment and are exposed to a multitude of occupational risks and hazards. Although many occupational settings harbour risks to employee health, Powell [4] notes how the cabin environment concentrates risk to individual health. Examples of exposures that occur in routine flight operations include poor cabin air quality from a number of sources; fatigue; cosmic ionising radiation; circadian rhythm disruption; high levels of occupational noise, pesticides; and infectious disease agents [3,[5], [6], [7]]. Cabin crew share the same workspace as pilots and are connected through interlinking roles. However, they remain an understudied field in the aviation/aerospace medicine and occupational health and safety literature [3,6,8,9].

Assessment of fitness for work is typically defined as “the evaluation of a worker's capacity to work without risk to their own or others' health and safety” [10]. The purpose of fitness-to-fly assessment is to describe the individual health state necessary for the performance of cabin crew duties, synthesising guidelines and regulations from national aviation administrative bodies [e.g. the U.S. Federal Aviation Administration (FAA)] and international agencies [e.g. the International Civil Aviation Organization (ICAO), and the International Air Transport Association (IATA)], as well as incorporating evidence-based and current scientific findings [11]. These medical standards aim to prevent the inability to perform the assigned duties and functions during flight operations that could be caused by the physical, medical and psychological disorders held by a crewmember [12,13]. To reflect working conditions and for the protection of the safety of the flight, airlines have a legal duty to ensure fitness for employment and to establish medical clearance procedures that are consistent and based on accepted physiological principles [[14], [15], [16]].

To ensure consistency with required medical standards, fitness-to-fly evaluations seek to detect existing medical conditions in pre-employment assessment and in recurrent medical checks for the existing workforce. Cabin crew must declare any new medical problem with potential safety ramifications, which develops during the period of employment [6,16]. Although fitness-to-fly attestation must specify the state of cabin crew health as a precondition for performing their work role [17], there are no current resources across the industry that provide harmonised tools for aviation medical examination, including guidelines for cabin crew to confirm point-of-time fitness.

Over the last two decades, the airline industry has undergone major reorganisation, and risks have changed. For cabin crew, the operational environment has undergone significant changes regarding extended flight times, increasing passenger loads, job insecurity, and exposure to new or re-emerging health risks [18,19]. For example, ultra-long-haul (ULH) flights have extended the time crew are exposed to a potential hazard, which in turn may pose greater risks. e.g. infectious disease transmission [20]. The detection of a novel coronavirus (SARS-CoV-2) leading to the illness COVID-19 demonstrated the rationale for adequate assessment for crew fitness-to-fly. For example, reports about cabin crew with COVID-19 operating domestic and international flights have raised questions about the safety of the exemption of the 14-day self-isolation rule [21]. Although clusters of confirmed cases are thought to have contracted COVID-19 while overseas rather than inflight, reports of in-flight transmission of respiratory infectious disease exist [22,23]. Importantly, Olsen et al. [24] note how a passenger travelling from Hong Kong to Beijing infected people well outside the WHO's two-row boundary, indicating that airborne transmission was likely the main transmission route for severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) in aircraft cabins. These reports further illustrate how air travel is an enabler of the rapid spread of newly emerging infections with pandemic potential. In the case of COVID-19 transmission may have occurred; either from passengers to crewmembers, among crewmembers, or infected crew members may have spread the infection to passengers and the wider public.

The airline industry and occupational health and aerospace medicine professionals need to be aware of the remitting nature of many health conditions, as well as the foreseeability of future states of poor fitness-to-fly. Past studies of the health of cabin crew have only been weakly matched to the demands of aviation regulators and aerospace medicine. For example, Mangili et al. [22] reported that cabin crew frequently fly when ill and typically have low vaccination rates. Substantial disparities exist between aircrews flying for U.S. regional carriers and European flag carriers relating to self-declaration when ill and routine influenza vaccination, with the rate of annual influenza vaccination ranging between 21 and 27% among aircrew [25].

Although the Centers for Disease Control and Prevention (CDC) and IATA consider it essential that aircrew are vaccinated against the common endemic diseases (such as measles-mumps-rubella, diphtheria-tetanus-pertussis, varicella, polio, and the seasonal influenza vaccine), and to keep vaccination records current [16,26], there are no established requirements for vaccinations in aircrew. Compulsory vaccinations may be based on country-specific entry requirements and include yellow fever [16,26]. Under the airline industry's plan to restart international air travel, Qantas further stated that vaccination for COVID-19 will be mandatory for travel for aircrew and passengers [27], raising the question of whether a similar policy will be administered industry-wide.

Several authors noted that stringent fitness-to-fly criteria, which apply to pilots, should also apply to cabin crew [7,17]; and that assessment criteria must be cognisant of the need to maintain flight safety [28]. Correspondingly, Griffiths and Powell [6] question whether statutory fitness-to-fly assessment will benefit either flight safety or occupational health, indicating that evaluations are deficient in the essential resources and components required to be effective. These views hinge on the notion that flight safety anchors on the success of uniform medical clearance, standardised training programmes, and a solid understanding of workplace exposure to hazards, for which the evidence base is currently insufficient and/or inconclusive. With passenger confidence largely resting on the assurance of hygienic conditions and healthy staff [29], auditing fitness-to-fly requirements amid the COVID-19 crisis is an opportunity to assess the operational usefulness of fitness-to-fly examinations; the scope and elements in flight operations; to implement changes; and to introduce remedial measures.

In this commentary, we present a novel viewpoint on fitness-to-fly to highlight externally imposed, and individually and socially generated factors that shape fitness-to-fly decisions. We discuss the implications of the rapidly evolving situation and future directions of the COVID-19 pandemic, including conceptual tensions that exist when managing operational fitness in cabin crew. In questioning whether selected medical criteria truly represent an impact on health and safety outcomes that matter most to flight safety and public health, we aim to promote scientific discourse that challenges the current approaches to fitness-to-fly evaluation. Derived from consistent themes in the aeromedical literature, the following sections discuss six major areas which require consideration to support existing fitness-to-fly evaluation.

2. Discussion

2.1. Statutory fitness-to-fly medical assessment

The requirements for fitness-to-fly assessment are based upon Standards and Recommended Practices (SARPs). These include recommendations published in the World Health Organisation (WHO) International Health Regulations (IHR); national legislation and regulations; airline-internal standards for medical assessments; and a fitness-to-fly medical guide for pilots, which is also applicable to cabin crew [11]. While the responsibility for cabin crew fitness is shared among the airline, aviation regulatory bodies and the crewmember, national aviation agencies are to ensure that airlines comply with their responsibilities in providing fit crewmembers. These agencies typically set requirements for aviation medical examiners (AMEs) to conduct fitness-to-fly evaluations. New cabin crew recruits require an initial medical examination, followed by periodic medical assessments at intervals of no more than 60 months [30].

If the purpose of fitness-to-fly is to achieve a balance between minimising any operation-related flight safety risks for the individual and the community posed by the crewmember's state of health, and maintaining the crewmember's occupational health, then any emerging risk to health should be accounted for. Given that international standards differ both within and between jurisdictions, as national airline regulators (such as the FAA) determine medical standards from their own jurisdictions [12,31], then this new assemblage of risks implies that new vulnerabilities are created that must be addressed through several medical dimensions that are underpinned by safety considerations.(See; Box 1, Box 2, Box 3, Box 4, Box 5, BOX 6 )

Box 1. Fitness-to-fly assessment in the context of COVID-19.

Adequate responses amid the COVID-19 crisis require cabin crew and airlines to know what employment actions are lawful in the face of a pandemic, and how staff can protect themselves as well as passengers. Until recently, the priority of travel health advice has not focussed on preventing the spread of infectious disease [32]. To prevent cases of infected cabin crew operating flights, IATA [33] recommends inclusion of self-certification statements from cabin crew, certifying the absence of COVID-19 symptoms when reporting for duty, or providing evidence of recent negative test results, “where rapid testing is available”. The challenge is to ensure that recommendations are a) adopted, b) implemented consistently by the airline industry, and c) do not carry any disciplinary actions if a crewmember reports unfit for duty. According to European Union Aviation Safety Agency (EASA) guidelines, aircrew should be exempt from an airport's COVID-19 screening procedures [34]; however. Some Australian states now require aircrews to take a COVID-19 test on arrival before self-isolating at home [35]. Other country-specific testing requirements include:

• -Cabin crew employed at Singapore carriers will be routinely tested for COVID-19 upon their return from overseas flights [36], and Singaporean aircrew travelling to China are required to undergo a pre-departure COVID-19 PCR test and IgM serology test [37];
• -Delta Airlines requires routine testing for COVID-19 before each tour of duty, using a rapid-response PCR test [38];
• -International aircrew arriving in New Zealand are mostly exempt from a 14-day isolation or quarantine period provided they meet certain conditions both inflight and during layover [39].

In addition, airlines will need to consider local requirements in the country of departure and arrival, and monitor local practices as they evolve with respect to immunity certificates or passports, or contact-tracking apps. While COVID-19 in and of itself will generally not affect fitness-to-fly, the mental effects of lockdown-related measures may impact a crewmember's decision-making ability and fatigue level [40].

Alt-text: Box 1

Box 2. Health concerns and risks of exposure amid COVID-19.

Cabin crew are at risk of contracting and/or transmitting infectious diseases. The high contact rates with interior aircraft surfaces among cabin crew and passengers can put crewmembers at infection risk and present a risk for public health [41]. Although the risk of onboard transmission remains unclear, transmission of SARS may have occurred inflight, when infected persons travelled during the symptomatic phase of illness [24]. High-efficiency particulate air (HEPA) filters may effectively limit the risk of airborne disease transmission inflight, but person-to-person transmission may carry the potential of causing clusters of infections such as influenza, SARS, tuberculosis and measles [22], and now potentially COVID-19 [42]. In addition, cabin crew must be able to recognise, characterise, and respond to various types of fumes, smoke or haze in the cabin environment [43]. For crewmembers that recovered from COVID-19, airlines must consider the impact of anosmia on their ability to identify atypical smells (e.g. chemicals or burning) [33]. Partial or complete smell recovery can last several weeks [44]. Elements to consider for fitness-to-fly assessment thus include novel types of diseases, which can imply previously unknown health risks.

Alt-text: Box 2

Box 3. Fitness-to-fly self-assessment and COVID-19.

By reporting for work, crewmembers declare themselves as fit-to-fly. Amid emerging public health threats, such as COVID-19, questions arise as to what extent do crewmembers consider their own risk factors in terms of early disclosure of underlying symptoms. IATA [33] has issued guidance for crew health precautions during pandemic noting that:

“Crew members must not report for training or flying duties if they:

• •Are within a mandated period of isolation or quarantine related to previous travel and/or duty;
• •Have tested positive for COVID-19 regardless of symptoms evident;
• •Know that they have been exposed to a person having, or suspected of having, symptoms of COVID-19;
• •Are experiencing symptoms of COVID-19;
• •Have recovered from COVID-19 symptoms but have not been assessed by the local Health Authority or the airline's occupational health program” (page 5).

IATA [33] further cautions against additional human factor concerns throughout the COVID-19 crisis, some of which may adversely affect crewmember health and performance, as well as introduce additional safety risks. For example, ongoing fear around employment uncertainty, infection, and protection may induce increased risk-taking to protect the operation, and lead to reduced reporting of noncompliance with procedures. For cabin crew, the difficulty in self-declaration may be in distinguishing between ‘compliance’, meaning they perceive themselves as being able to function (albeit at the expense of their own health), and ‘non-compliance’ that potentially compromises flight safety or public health by not being able to foresee the consequences of their impaired state of health.

In addition, EASA [34] has advised airlines to provide operational recommendations to minimise the risk of infection of cabin crew during layovers. Airlines should further inform crewmembers that the most efficient preventive measure to limit the potential transmission of SARS-CoV-2 from contaminated surfaces is frequent handwashing [45]. In practice, this may prove challenging due to the lack of designated crew handwashing facilities [46,47]. While crewmembers may carry their own disinfectants to ensure an additional layer of protection, the EASA has advised against the use of personal disinfectants in the aircraft cabin. Surfaces disinfected with self-provided products may cause corrosive reactions with chemicals used for general disinfection agents which can have damaging effects on the aircraft or lead to adverse health effects for passengers and crew [48]. Cabin crew must therefore rely on company enforcement and appropriate application of disinfection procedures.

For crewmembers reporting fit-for-duty, questions include whether and how IATA and EASA recommendations are communicated to cabin staff, and what monitoring systems are in place to check crewmembers' reporting behaviour. Importantly, could reporting for duty resemble a safety breach in the case of a knowingly unwell state of health? Reporting for duty behaviour may largely be based on individual perception of health and safety, which resonates that perceptions may influence reporting or not reporting for work decisions stronger that objective variables. Depending on the type and length of flight sectors, or type and length of layover, other factors may also influence the decision of reporting fit-for-duty (e.g. the quality of health services available at a layover destination). The self-declaration form developed by the Collaborative Arrangement for the Prevention and management of Public Health Events in Civil Aviation (CAPSCA) [49], and the “I'm safe checklist” developed by the FAA for pilots [50] could be useful tools to help with self-assessment. In this way, cabin crew may become more aware of their innate capacity to report fit-to-fly, and could better recognise the importance of safety and regulatory concepts deemed important not only for their own health, put for the wider public.

Alt-text: Box 3

Box 4. Public perfections of a healthy workforce amid COVID-19.

One purpose of fitness-to-fly is its social value, understood as its ability to produce the conditions needed to ensure safe flight operations. The return to air travel hinges on trust, and will fall on the airlines to reassure air travellers that it is safe to fly. Although IATA recommendations bear no legal grounds for enforcement, they make a strong claim to best practice and authority relating to IATA's core principles on passenger protection [51]. Another component is feasibility: Fitness-to-fly must have a credible prospect of meeting its purpose while scientific evidence is still lacking. The historical distinction between work and non-work exposures has become less useful in understanding risks. As globalization has exacerbated poor regulatory oversight [52], airlines must re-consider their own risk assessment processes and compliance mechanisms for fitness-to-fly reporting to ensure cabin crew do not report for work unwell. With passenger confidence largely hinging on the assurance of hygienic conditions and healthy staff amid the COVID-19 pandemic [29], airlines should further monitor whether any COVID-19 control measures have introduced new problems, e.g. the use of gloves and masks when responding to an inflight medical case.

Alt-text: Box 4

Box 5. What is beneficial to all stakeholders amid COVID-19.

How far the ideal of fitness-to-fly standards corresponds to the practices of self-assessment during the COVID-19 pandemic remains debatable. Airlines should consider the possibility that reporting behaviours may reflect an underlying dimension of response to a work situation. Illnesses, or patterns of illnesses, are typically picked up by frequent supervisory observations or work performance checklists, providing an indication of a health issue [10]. However, these are difficult to observe in the cabin crew workforce due to frequent changes in crew formation. Ground supervisors for cabin crew typically do not see crewmembers very often, putting the bulk of responsibility on the individual to be self-critical and to manage their health well. To ensure that unfitness does not escape regulation altogether, airlines and crewmembers could further benefit from systematic response systems to address individual health issues that require monitoring. Holistic approaches that examine all potential factors that can influence cabin crew health, alongside the promotion of a non-punitive reporting culture to not sabotage their own health, will go a long way towards maintaining a healthy workforce, which can benefit all stakeholders.

AMEs vouch for a crewmember's flightworthiness [11]. Consequently, careful health assessment of cabin crew is of the same vital importance as that of pilots, and would benefit from an improved understanding of the social and legal contexts affecting cabin crew health. This would involve incorporating information related to the economic context of airline organisation; impact of health on business sustainability; the relationship between flight operations and health disparities into existing fitness-to-fly evaluations; and putting into place improved oversight frameworks for examiners to balance medical confidentiality and safety. By allowing connection of medical records to the aviation medical examination process (beyond self-reporting), privacy may have to take a backseat to safety in some cases to allow reassurance of good health.

For the public, fitness-to-fly requires demonstration rather than mere assertion. Failure to protect the public from unfit staff can entail significant liability for airlines [53]. Medical evaluation should include assessments of the safety risks associated with a crewmember reporting for duty unwell, be proportionate to the public health risk, and be reconsidered regularly as new hazards evolve. Follow-up measures such as performing cabin crew testing after an illness, or after rehabilitation measures, could act as additional layer to benefit flight safety. Significant benefits may be gained from developing perspectives on fitness-to-fly that focus not only on physical functions, but on the protection of public health.

Environmental and operational contexts attract causal factors that go beyond current knowledge. To maintain a healthy workforce, which can benefit all stakeholders, integration of up-do-date scientific evidence and continuous dialogue with all stakeholders is essential to further strengthen the aeromedical assessment system. Such research can further assist in gaining a better understanding of how passengers perceive the need for a healthy workforce.

Alt-text: Box 5

BOX 6. Fitness-to-fly theory in the context of COVID-19.

To better understand the inherent dynamics of fitness-to-fly amid COVID-19, we distinguish basic constituents of the assessment system and the drivers of operational features, as well as occupational and environmental change. This relates to technological development that has often outpaced scientific knowledge related to the determinants of health [54], as well as the nature of the operational setting and physical condition of a crewmember that may modify susceptibility to exposures inherent to their activities [55]. While this theory may explain why the alignment of fitness-to-fly with medical standards and operational practice is not absolute, it may imply that crewmembers compensate for any fitness deficits by retreating into non-compliance spaces divorced from the safety concept. Consequently, the collective basis of fitness-to-fly and thus the capacity for operational resistance is abstracted from the employment relationship rather than being integral to its contested nature. We see the essential feature of fitness-to-fly as the notion of risk due to unforeseen events and ad-hoc changes which should incorporate more precise operationalisation of the probability of harm and better explain the relationship between fitness, illness and perception of health status. This approach does not ascribe to any belief system but offers powerful ways for self-assessment: pre-flight fit-check analysis engages the knowledge production about fitness-to-fly on which many aspects of contemporary assessment practices are predicated. Fit checks thus aim to act as vehicle for cabin crew to minimise chances of reporting for work unwell, and to give them a feeling of serenity, especially in the sphere of uncertainty. The fit check can be used to parsimoniously engage, educate and promote proactive, positive fitness-to-fly activities to cabin crew.

Alt-text: BOX 6

2.2. Cabin crew: exposure to risks and hazards and general health concerns

For cabin crew, reported occupational injuries and illnesses represent only a fraction of the true events [56,57]. The impact of work-related psychosocial factors is even less understood [58,59]. Risk assessment frameworks toward cumulative risk assessment have recognised that exposure to a single hazard rarely occurs in isolation [60]. Examples for exposure risks include:

• •Pesticide use in aircraft cabins to control the spread of vector-borne diseases

Although Pang et al. [61] found no evidence of an association between crew exposure to certain insecticides and negative health impact, uncertainty remains about the potential adverse health effects on human health in the absence of longitudinal exposure assessment that correlate insecticide exposure (including carrier substances) and physiological uptake of insecticides to possible toxicity [20]. In addition to cumulative exposure to contaminants, researchers must explicitly measure the association between different types and levels of exposure and ill-health symptoms [62].

• •ULH operations

The longer crews are exposed to a hazard, the greater the likelihood that harm may result. This also applies to determinants of fatigue. Originally designed to accommodate unpredictable factors such as delays or weather conditions, reduced-rest patterns under ‘exceptional conditions’ have become increasingly common [18]. This requires consideration and management of the interactive effects of workload and fatigue [63].

• •Foodborne and respiratory disease

Reports of likely transmission of norovirus from symptomatic cabin crewmembers to passengers [64] illustrate how crewmembers may also act as reservoir for pathogen transmission, such as in their role as food handlers [65]. Similarly, an ill cabin crewmember could pass on a respiratory illness to passengers or to other crewmembers. For example, for influenza A (H1N1), the potential for inflight transmission has been calculated at five to ten infections which could occur during an 11-hr flight, if the index case travels in economy class [66]. WHO guidance purports that the primary inflight transmission risk for most respiratory infectious diseases is sitting within two rows of an infectious passenger [67,68]. However, this guidance does not directly take into account the biological bases of droplet transmission and indirect contact via fomites, and does not account for the movement activities of seated passengers and crew which can significantly increase infection risks [69]. Depending on their movements and interactions with passengers, Hertzberg and Weiss [23,70] note the probability of an infectious crewmember to infect several passengers. Potential modes of transmission include contact occurring in waiting areas (e.g. near galleys where cabin crew work), indirectly through contact with contaminated fomites, or through airborne transmission which was likely the main transmission route for SARS-CoV-1 in aircraft cabins [24] (See Box 2 ).

2.3. Fitness-to-fly self-assessment: to fly or not to fly?

Reporting fit-for-work is an individual responsibility [71]. Similar to how a designated physician can refuse transport to a person with acute illness that might compromise the overall safety of the flight [72], cabin crew become their own assessor upon reporting for duty – directed by their perceptions of what makes them fit or unfit for work. Cabin crew showed a higher prevalence of work-related upper respiratory tract symptoms, colds and influenza compared to the general working population, and were less likely to report medically diagnosed asthma [73]. For mental health symptoms, self-disclosure is often affected by fear of stigma and discrimination [74]. Calling in “sick” also interrupts the planned schedule, which can create new disruptions elsewhere in the schedule [75], and potentially invite undesirable changes. If reporting fit-to-fly is an individual responsibility, then discussions require a hands-on definition of the aspects of fitness-to-fly that appear to be signifiers of flight safety, including potential implications on flight operations and the health of others in the case of unfitness-to-fly. Table 1 presents examples of cabin crew perceptions on fitness-to-fly, extracted from an online blog analysis (See Box 3 ).

Table 1.

Fitness-to-fly: Cabin crew perspectives and resulting questions for research.

Online blog results	Research questions
Crewmembers perceived fitness to fly assessment an activity in its own right; “an inconvenient annual procedure that just has to be ticked off”	Are decisions about which health issues are risky enough to justify ‘unfitness’ driven by safety considerations? What procedural changes in assessment would increase crewmembers' confidence in fit-to-fly attestation? Does ‘good overall health’ resemble fitness-to-fly?
Cabin crew form a health perception score of a particular flight based on their perception of flight-specific risk attributes. To arrive at a decision of reporting fit or unfit to fly, this score is in turn traded-off against other flight operational attributes, such as type of layover or potential schedule disruption	Would self-reported health-related incidents provide some evidence as to the effectiveness of the scheduling tool? What motivates crewmembers to exhibit safe or unsafe behaviour?
Crewmembers often override concerns over making a poor decision with a “can do” attitude, despite the presence of ambiguous cues, goal conflicts, and uncertain outcomes by presenting for work	What can improve crewmembers' ability to judge their fitness upon reporting for work? Through which processes do cabin crew assess their fitness, report or not report for work, and consequently adopt curative and/or preventive measures?
Organisational norms, values, safety culture and punitive measures influence cabin crew's decision-making when reporting for work	What aspects of an organisational safety culture and scheduling practices could foster ‘genuine’ decision-making? Would supportive re-scheduling reduce triggers towards what crewmembers term “organisational punishment?”
Cabin crew largely perceive occupational hazards and associated risks to be beyond their control	Would scientific clarity over exposure to risks improve cabin crew attitudes towards the controllability of health and safety? What knowledge do cabin crew have about disease transmission and what is their perception of severity and risk of certain infectious diseases?
Cabin crew have poor trust in scientific evidence airlines use to address exposure to hazards and concerns about staff health	Would crew participation in research efforts improve trust issues?
The pervasive culture of fear and punishment at some airlines creates a bias against disclosing a medical issue to the organisation	At what point do attestations from general practitioners declaring a crewmember unfit to work have to be shared with the airline's medical department to get a sense of the severity of a condition? When to AMEs need to disclose the nature or intensity of a health condition?

2.4. Public expectations of cabin crew health

Fitness-to-fly is a conceptual construct that can also be employed in the interests of the public. Airline safety and reliability are the most important determinants in passengers’ airline choice and travel behaviour [76,77]. Passengers are the stakeholders most concerned with the outcomes of the aviation medical assessment system; they generally trust that airlines place value on the health and safety of its workforce [78]. Health assessments must therefore exceed standard practices and move beyond mere compliance with regulations (designed to prevent failure), to a best practice approach based on trust and verification. For example, research could explore whether additional health screening procedures (such as testing cabin crew for COVID-19), or requirements for crew to wear masks, would make passengers feel safer. (See Box 4 )

2.5. What is beneficial to all stakeholders?

All stakeholders want and need the cabin crew to be truly fit-to-fly. Fitness-to-fly assessment must therefore remain responsive to addressing the concerns all of stakeholders. While airlines may be primarily interested in meeting the statutory requirements of establishing a point-of-time medical clearance procedure, Griffiths and Powell [6] call for an evidence-based, international approach to fitness-to-fly concerns so that priorities and responsibilities can be set in a transparent manner, and parameters made internationally uniform. If a crewmember can be either fit or unfit-to-fly, then the identification of threats in the full operational context becomes paramount for policymaking. This requires determining effective risk mitigation processes which support the cabin workforce and passenger confidence. Examples include the increasing the evidence base on inflight transmission risks for infectious diseases [32,79], and identification of methods for crew to validate their status upon reporting for duty. In addition, health authorities should ensure to include cabin crew in the case of disease tracing and not restrict contact tracing based on seating proximity or flight duration [80] (See Box 5 ).

3. Conceptual considerations

From an aeromedical perspective, it is helpful to conceptualise the potential impact of any risk associated with poor fitness that could result in the potential for harm [81]. Fitness-to-fly can be conceptualised as defining element of both professionalism and error; involving complex, layered constellations that have resulted in novel empirical processes that are productive of unfitness-to-fly. As such, fitness-to-fly appears to be a concept of faith in the individual's medical assessment, one that exists in a virtual realm, rather than an operational reality. The problem with this application is that it does not explain the purposiveness of fitness-to-fly assessment; it presupposes it. Theoretical motives behind fitness-to-fly should thus be formed by factors that pull toward potential and foreseeable events, rather than pushing from an experienced past. Such approaches move from statutory medical clearance, which carries the risk for fitness-to-fly to be perceived as symbolic attestation of a “blank cheque for a certain period's worth of good health”, to an extension of assessment protocols in the form of a pre-flight fit check. The conceptual spheres for fitness-to-fly are depicted in Fig. 1 (See Box 6 ).

Fig. 1.

Key spheres of the concept of Fitness-to-fly.

In addition, we suggest five thematic intersections between fitness-to-fly, occupational and public health, and flight safety:

• (1)National regulation;
• (2)Spaces of airline-specific regulation and assessment;
• (3)Health monitoring and maintenance;
• (4)Environmental factors; and
• (5)Individual vulnerability and coping capacity.

To support a harmonised approach, these intersections require formal mutual acknowledgment of national regulatory bodies, airlines, and AMEs.

4. Conclusion

Through the COVID-19, crisis the airline industry illustrated the operational purpose for fitness-to-fly, and how changes in hazards alter the nature of risk to the cabin crew workforce and the travelling public. Significant gaps in risk assessment for known risks remain unaccounted for and the emergence of new occupational risks requires a review of risk assessment. The uncertainty created by the COVID-19 pandemic is a reminder that fitness-to-fly evaluations require an observant state of mind. To achieve a sustainable decision on fitness-to-fly is not primarily a medical responsibility, but requires globally harmonised, and mutually accepted criteria for evaluation. These criteria should be compatible with safety requirements; proportionate to the exposure to occupational hazards and risks; flexible where appropriate to allow for a specific exception; and safeguarded not to discriminate.

The analytical angle of fitness-to-fly is informed by various disciplines, rendering it valuable to scholars from medical to aviation studies, as well as to those from tourism. Exploring the operational make-up of fitness-to-fly makes an important contribution to the literature. It enlarges the remit of aviation risk management research to a more complicated field constituted not just by the most visible outcomes (i.e. incidents and accidents), but also by a host of covert health threats. Just as how safety in aviation has consolidated standards among international airlines, the arrangement of ancillary functions such as ‘health safety’ must likewise be recognised for its indispensable role in supporting fitness-to-fly and safety goals towards safe travel outcomes. It is by tracing these complex spaces for fitness-to-fly that the true pervasiveness of global air travel can be apprehended, along with a fuller appreciation of its impacts on populations in terms of disease transmission and spread. Delineating the pragmatics of fitness-to-fly production affords added insight into recent analyses depicting air transport as main driver in the frequency and reach of infectious disease epidemics.

CRediT authorship contribution statement

Andrea Grout: Conceptualization, Methodology, Literature search, Writing - original draft. Peter A. Leggat: Writing - review & editing.