Introduction
Air travel is now a routine part of working life for many employees, including business travellers, offshore and maritime workers. Aeromedical issues also apply to those working in the aviation sector and those involved in drone and remotely piloted aircraft operations. Occupational health (OH) professionals may be asked to advise on fitness to fly, manage health risks associated with air travel, and assess workers whose roles have aviation safety implications.
While aviation medicine is a specialist field, many of its principles overlap with core OH practice. A working understanding of the physiological, psychological, and regulatory aspects of flight can help OH clinicians provide clearer, safer, and more consistent advice. This article outlines key aeromedical issues relevant to occupational health.
What Does “Fit to Fly” Mean?
The term fit to fly is often used imprecisely. It may refer to fitness to travel by air as a passenger, or fitness to perform a specific role during flight, such as pilot, cabin crew member, or air traffic controller.
These meanings are not interchangeable. An individual may be fit to fly as a passenger but not fit to undertake aviation duties. OH advice should therefore be role-specific and journey-specific, taking into account flight duration, aircraft type, altitude exposure, and lack of access to medical support.
Physical Hazards of Air Travel
Commercial air travel exposes individuals to reduced barometric pressure, vibration, noise, cold, and relative immobility. Pressure changes may cause sinus, middle ear, or dental issues.
Relative immobility, particularly on flights longer than four hours, is associated with an increased risk of venous thromboembolism (VTE), estimated at approximately 1 in 6,000 passengers. Risk mitigation includes regular movement. There is no evidence to support routine aspirin use for travel-related thromboprophylaxis. Compression stockings or anticoagulation may be appropriate in selected higher-risk individuals following specialist haematology assessment (NB over-the-counter compression stockings are not the same as surgical compression stockings).
Figure 1
Physiological Effects of Altitude
At sea level, atmospheric air contains approximately 21% oxygen, but oxygen delivery depends on the partial pressure of oxygen, which decreases with altitude as barometric pressure falls. Commercial aircraft cabins are pressurised to the equivalent of around 6,000–8,000 feet. Although oxygen concentration remains unchanged, reduced partial pressure leads to lower alveolar and arterial oxygen tension.
Healthy individuals compensate through increased ventilation and cardiac output. Those with respiratory or cardiovascular disease, anaemia, or reduced physiological reserve may have limited compensatory capacity. Symptoms of altitude-related hypoxia include dyspnoea, fatigue, headache, impaired concentration, impaired colour vision and even collapse.
The oxygen–haemoglobin dissociation curve, see Figure 1, explains why small reductions in oxygen pressure at cabin altitude can cause clinically significant desaturation in susceptible individuals. Those with pre-existing hypoxaemia may operate on the steeper portion of the curve, where small pressure changes lead to disproportionate falls in oxygen saturation. This underpins the need for careful clinical assessment and, in some cases, in-flight supplemental oxygen, guided by specialist advice such as the British Thoracic Society guidance on air travel
https://www.brit-thoracic.org.uk/quality-improvement/clinical-statements/air-travel/
Altitude physiology also intersects with emergency egress. Rare evacuation events demonstrate that smoke exposure, cognitive impairment, limited mobility and normal human behaviour can significantly affect survivability. Conditions impairing cardiorespiratory reserve, cognition, vision, or mobility may therefore be relevant not only for routine travel but also for emergency scenarios.
Cosmic Radiation
Exposure to cosmic ionising radiation increases with altitude, latitude, aircraft type, and flight duration. A transatlantic flight delivers approximately 0.08 mSv, compared with an average UK annual background dose of around 2.7 mSv.
Under the Ionising Radiation Regulations 2017, workers exposed to radiation in the course of their duties require appropriate risk mitigation, with particular consideration for pregnant workers. For occasional business travellers, exposure is small, but OH professionals advising frequent flyers should be aware of cumulative exposure and regulatory responsibilities.
Biological and Chemical Hazards
Aircraft cabins are enclosed environments, raising potential concerns about airborne infection transmission. Modern ventilation systems are highly effective, and infection risk is best managed using standard public health principles.
Hypoxia remains the principal chemical hazard of flight. The concept of aerotoxic syndrome is occasionally raised but remains controversial, with limited supporting evidence.
Psychological Hazards
Jet Lag
Jet lag results from circadian rhythm disruption and commonly presents with insomnia, fatigue, gastrointestinal disturbance, and impaired cognitive performance. Westward travel is generally better tolerated than eastward travel, with recovery taking approximately 1–1.5 days per time zone crossed. Daylight exposure and sleep scheduling are key management strategies. Melatonin may benefit some individuals but is not licensed in the UK.
Flying-Related Anxiety
Flying anxiety ranges from mild anxiety to true phobia. Common fears include crashing, confinement, loss of control, and the unknown. Management may include behavioural strategies or fear-of-flying courses. Benzodiazepines are generally not recommended due to impaired reaction time, paradoxical effects, interaction with alcohol, and reduced ability to respond in emergencies.
Medical Support in Flight
Commercial aircraft carry Emergency First Aid Kits for cabin crew use and Emergency Medical Kits, which may be opened only with the captain’s authority and are intended for use by medical professionals. Equipment and medications are limited and vary by regulator/operator/aircraft.
Most airlines have access to ground-based medical advisory services, such as MedAire or MedLink, providing real-time advice and guidance on diversion decisions. In-flight medical care should not be equated with hospital-level support.
In-Flight Incapacitation and Medical Diversions
Despite preventive measures, in-flight incapacitation can occur. Screening opportunities include pre-flight medical declarations and informal observation at check-in or boarding.
Medical diversion decisions are made by the aircraft captain, informed by medical advice. Considerations include the suitability of diversion airfields, availability of medical facilities, aircraft performance limitations, and fuel management. These factors may be relevant when advising employers on travel planning for employees with complex medical conditions.
Regulatory Medicine and Occupational Roles
Aviation medicine is regulated by bodies including the UK Civil Aviation Authority (CAA), EASA, ICAO, and IATA, underpinned by UK legislation such as the Air Navigation Order 2016 and UK Part-MED regulations.
Pilots and Air Traffic Controllers
Medical certification is regulated by the CAA and undertaken by approved Aeromedical Examiners (AMEs). Applicants are considered unfit until evidence demonstrates the required standard is met, reflecting the very low acceptable risk of incapacitation.
Cabin Crew
Cabin crew medical standards are regulated by the CAA and may be assessed by AMEs or authorised occupational health medical practitioners. Standards are broadly comparable to DVLA Group 1, with a higher acceptable incapacitation rate due to team-based working.
Drone Operators
Medical requirements for drone operators are outlined within CAA CAP 722 https://www.caa.co.uk/data-and-publications/publications/documents/content/cap-722/. These emphasise fitness principles similar to those applied to driving and represent an expanding area of OH practice.
Conclusion
Aeromedical issues intersect with occupational health more frequently than is often recognised. While specialist aeromedical assessments remain the responsibility of those with the appropriate skills, OH professionals play a key role in advising on fitness to fly, managing travel-related risk, and supporting employers in policy development. A practical understanding of aviation-related hazards and regulatory frameworks can enhance the quality and safety of OH advice.
Dr Clare Hunter is an occupational physician with experience across military maritime and aviation, commercial aviation, the NHS, and local authority sectors. A former GP and CAA Authorised Medical Examiner, she now works as an independent practitioner and part-time with EOPH. She holds the Diploma in Aviation Medicine and is currently undertaking an MSc in Organisational Psychology, with an interest in human factors and safety-critical work.
