Provide Tailored Advice on Fitness to Fly

Dr Peter Saul Sets Out the Key Considerations to Make When Assessing an Adult’s Fitness for Air Travel, Covering a Wide Range of Conditions

In 2024, as tourism and confidence continue to recover after the COVID-19 pandemic, Britons are expected to make an estimated 86.9 million overseas visits—this will surpass the 84.7 million visits made in 2019, the year before the pandemic.^1,2 European data also indicate that people aged 60–74 years are taking longer trips and travelling more intensively than others, likely because of the time available to them following retirement.³

With foreign travel rebounding and given the increased average age of travellers, GPs and their teams are likely to be asked for advice concerning fitness to travel more often, particularly by individuals with chronic illness. When offering such advice to potential travellers, there are three main elements to consider: what they are planning to do, where they are planning to visit, and how they are planning to get there. This article will focus on the last point—specifically, the health aspects of air travel, including physiological and practical considerations, additional measures that may need to be taken, and conditions that preclude regular commercial flight.

This article is based primarily on guidance offered to healthcare professionals by the UK Civil Aviation Authority (CAA) on how to assess fitness to fly.⁴ This guidance is supplemented by the Aerospace Medical Association (ASMA)’s Medical considerations for airline travel⁵ and the Medical manual provided by the International Air Transport Association (IATA).⁶ 

Stresses of Flight

The stresses of airline travel start well before boarding the aircraft, as modern airports have become increasingly hostile environments, with long distances to traverse, security checks, limited seating, queues, and frequent delays.⁷ During flight, the main stresses are limited space and mobility, noise, vibration, reduced humidity, and lowered barometric pressure in the cabin at altitude.^7,8

Air Pressure

Most aircraft cabins are pressurised to between 5000 ft and 8000 ft (more modern aircraft, such as the Boeing 787 or the Airbus A350, are pressurised to the lower end of this scale).⁹ This adjusted barometric pressure causes a reduction in the partial pressure of oxygen, in turn decreasing arterial oxygen pressure (PaO₂)—from sea level to 8000 ft, the reduction is from about 98 mmHg to 55 mmHg.⁷

Blood oxygen saturation will typically fall to approximately 90% at this altitude, and healthy travellers can compensate for this relative hypoxaemia well.^7,10 However, in people with respiratory, cardiovascular, or cerebrovascular disease or anaemia, this may not be the case.⁷ Instead, because of their underlying reduced PaO₂, these people may reach more severe oxygen desaturation, and experience an exacerbation of their condition.^7,11

Reduced cabin pressure also causes the expansion of any enclosed air spaces in or around the body by approximately 30%, and travellers who have upper respiratory tract infections may experience sinus or ear pain as a result.¹⁰ For people who have recently undergone surgery in which gas has been trapped or introduced into the body, there may be serious complications related to this expansion, and flight can be contraindicated for up to 6 weeks (depending on the surgical circumstances).^10,12 For similar reasons, care must be taken to avoid travelling with a recently applied closed plaster cast, for fear of issues relating to swelling and pressure under the cast—most airlines require passengers to wait as long as 48 hours after a cast is fitted (24 hours for flights lasting less than 2 hours).^12,13

Low Cabin Humidity

Potential dehydration due to low cabin humidity is easily compensated for with normal, or increased, fluid intake; however, the effects on the cornea and airways are more difficult to manage.⁷

Limited Space

As typical seat pitches are seldom above 32 inches in economy class and high-density seating,¹⁴ the lack of mobility can potentially exacerbate peripheral oedema, reduce circulation, and increase the risk of deep vein thrombosis (DVT).⁷

Considerations by Disease Area and Condition

The rest of this article concerns advice that primary care practitioners can give to their patients relating to pre-existing conditions. The key conditions for which flight should be avoided are outlined in Table 1.^15–18

Table 1: Contraindications to Commercial Airline Flight^15–18

Cardiovascular Disease

Cardiovascular disease (CVD) is the disease area about which patients are most likely to seek advice from their GP regarding fitness to fly¹⁶—see Table 1 for cardiovascular conditions in which flight should be avoided. The main concerns identified by the CAA relate to relative hypoxaemia in flight, which may trigger significant physiological responses.^16,19 A fall in arterial oxygen saturation can lead to an increase in ventilation and mild tachycardia, and therefore a rise in myocardial oxygen demand.¹⁶ The majority of people with CVD—including those with controlled hypertension or stable angina, and those who have recovered from coronary interventions—should have no problems when travelling, but they should be cautioned to carry any relevant medications on their person.¹⁶ People with heart failure may be difficult to assess, but evidence suggests that flights of 7 hours or less are tolerated by those with mild-to-moderate stable heart failure (equivalent to the New York Heart Association grade II),¹⁹ with more serious heart failure being considered an indication for the use of supplemental oxygen in flight.¹⁶

Some people with CVD may require supplemental oxygen (see Supplemental Oxygen, below), including those with cyanotic congenital heart disease, primary pulmonary hypertension, or other CVD associated with known baseline hypoxaemia.¹⁶

Respiratory Conditions

The relative hypoxia caused by reduced cabin pressure also affects people with respiratory conditions, and a significant portion of more serious in-flight medical emergencies are respiratory in nature. The British Thoracic Society (BTS) issued updated guidance on this topic in 2011, noting that respiratory events in passengers are the subject of around 10–12% of in-flight radio calls for emergency medical assistance.²⁰ The BTS offered further advice in a clinical statement published in 2022, with a summary appendix specifically for primary care practitioners.^18,21

The BTS statement identifies only four contraindications to air travel (see Table 1), but fitness to fly may need to be considered in anyone with chronic pulmonary disease.^18,20 Assessment, with history taking and examination, is recommended for people with a number of respiratory conditions.¹⁸ Of them, the main groups that are most likely to approach GPs are those with:

• asthma, chronic obstructive pulmonary disease, or another form of airflow obstruction
• interstitial lung disease, or another form of restrictive respiratory disease
• respiratory infections.

Other groups identified by the BTS, but who are likely to be under specialist care and are best advised by their hospital consultants, include those with:¹⁸

• bronchopulmonary dysplasia, cystic fibrosis, bronchiectasis, pulmonary hypertension, or venous thromboembolism
• recent thoracic surgery or other interventional procedures
• pleural disease, such as pneumothorax or pleural effusion
• obstructive sleep apnoea syndrome
• lung cancer, including mesothelioma.

Supplementary Oxygen

Some people may require supplemental oxygen (see Box 1).^16,18,20,22 If there is any doubt about whether a person may require in-flight oxygen, specialist assessment is advised; a hypoxic challenge test may be required as part of this assessment.^18,20

Travellers may be able to request the provision of supplemental oxygen by the airline or take their own portable concentrator or bottled supply, but in all cases will need to make arrangements in advance.^6,16,18,19 Aircraft emergency oxygen is not suitable or available for medical use. 

Any request to an airline for oxygen or other medical equipment, or for a traveller to use their own oxygen concentrator, needs to be made on a designated form such as the IATA Medical Information Form for Air Travel (MEDIF), which will require considerable clinical detail.^6,20 These are usually supplied by individual airlines—an example can be found on the CAA website.^6,23

Ear, Nose, and Sinuses

As pointed out in the ASMA guidance, the external- and middle-ear passageways need to be fully open to allow for pressure changes during flight.¹⁷ Any recent surgery or active acute or chronic ear conditions, such as middle-ear infection, may cause problems and will likely need to be assessed by a healthcare professional before flight, in some cases by an otolaryngologist (see Table 1).¹⁷

To allay the risk of obstruction of the sinus ostia and prevention of pressure equalisation, ASMA also recommends that flying should be avoided in people with sinusitis (acute or chronic), large polyps, recent nasal surgery, recurrent epistaxis, or a significant upper respiratory tract infection.¹⁷ The guidance warns that flying with these conditions ‘can lead to severe headache, facial pain, orbital or central nervous system (CNS) sinus disease extension, or bleeding’.¹⁷

Diabetes

The CAA emphasises that air travel should not present significant problems for individuals with well-controlled diabetes.²⁴ However, adequate medication and equipment should be carried with the passenger.^24,25 Ideally, insulin should be kept in the cabin, as there is a risk of loss and exposure to temperatures that facilitate its degradation when insulin is stored in the hold.²⁴ Insulin can be transported in a cool bag for long-haul flights.^24,25

Medication timing may be affected by travel across time zones, particularly if the travel day is effectively changed by 2 hours or more, and will need to be adjusted accordingly.²⁴ For people travelling east, the day is effectively shortened, and it may be necessary to take fewer units of insulin that are intermediate or long acting.^24,25 Conversely, travelling west effectively extends the day and may necessitate an extra meal and supplementation, such as with additional injections of short-acting insulin or an increased dose of an intermediate-acting insulin.^24,25 These considerations can be particularly critical for type 1 diabetes.

People using insulin pumps may also experience minor changes in insulin delivery as a result of pressure changes during ascent and descent.^7,24

Haematological Disorders

With haematological disorders, the main concern is reduced haemoglobin concentration,²² which may result in significant hypoxaemia at altitude. Special assessment is required, and supplemental oxygen may be necessary, for individuals whose haemoglobin level is below 7.5 g/dl.²²

People with sickle cell trait are unlikely to experience problems with air travel, but people with sickle cell anaemia should travel with supplemental oxygen and defer travel for approximately 10 days following a sickling crisis.²²

DVT

Travel-associated DVT is a particular risk when travel duration is 4 hours or more.²² Simple measures, such as moving about the cabin and performing leg exercises, can be prophylactic, and individuals with high underlying risk should be considered for anti-embolism stockings or low-molecular-weight heparin.²²

Mental Health Conditions

Regarding travel after a psychiatric diagnosis, the CAA emphasises that the most important things to consider are whether the person’s condition may interfere with the safe conduct of the flight, and whether the flight environment may exacerbate their condition.²⁶

Pregnancy

The Royal College of Obstetricians & Gynaecologists (RCOG) provides detailed guidance on air travel and pregnancy.¹⁵ The RCOG emphasises that the main concern for airlines is the risk of labour developing in flight.¹⁵ Consequently, most airlines do not allow women to fly after the 36^th week of gestation for a singleton pregnancy, or after the 32^nd week for women with risk factors for preterm labour, such as a multiple pregnancy or a history of preterm labour.¹⁵

If a woman has a history of miscarriage or ectopic pregnancy, the guidance advises establishing the location and viability of pregnancy by ultrasound before travel.¹⁵

There are no good data to suggest that commercial airline travel is associated with an increase in the risk of adverse pregnancy outcomes, such as preterm labour, preterm rupture of the membranes, or placental abruption.¹⁵ The risks to the fetus of the reduced partial pressure of oxygen are negligible because of the higher red blood cell count of the fetal circulation and the greater affinity for oxygen of fetal haemoglobin.¹⁵ Increased exposure to cosmic radiation is not considered a significant cause of maternal or fetal risks for occasional flights, and exposure to radiation from security body scanners is considered negligible.¹⁵

Summary

Although commonplace, air travel can pose risks to vulnerable individuals, especially those whose health conditions may be affected by reductions in PaO₂ or atmospheric pressure. In general, most people can be advised that air travel will be safe providing that their symptoms are stable, although it is best if they are reminded to carry sufficient medication in their hand luggage and ensure that they have appropriate medical insurance. When there is any doubt about safety, or guidance suggests that a more detailed assessment is required, travellers should seek advice from the relevant specialist.

Primary care practitioners should also advise their patients to discuss any special needs with the airlines themselves before their flight. GP letters detailing a person’s medication and treatment delivery, such as insulin, inhalers, or adrenaline auto-injectors, are helpful—not least from a security point of view—but more detailed medical information will need to be supplied on a MEDIF.