Fitness to fly and inflight medical events

Last updated: December 1, 2022

Summarytoggle arrow icon

The combination of an ongoing global increase in airline passengers and an aging population with more comorbidities means increasing numbers of patients with preexisting medical conditions are traveling by air. [1] Basic knowledge of how to assess fitness to fly on commercial airlines and how to respond to inflight medical events is therefore of increasing relevance to clinicians.

Space medicine is the practice of medicine on astronauts during spaceflight and involves the prevention and treatment of common illnesses in space. Stressors unique to space include effects of microgravity, spatial confinement, and limitations of remote help. There is a strong emphasis on prevention and preflight screenings because of limited medical equipment, diagnostic capabilities, and medications during spaceflight.

Fitness to flytoggle arrow icon

  • Clinicians may be asked by the airline to provide a “Medical Certificate” regarding their patient's fitness to fly.
  • The International Air Transport Association (IATA) recommends that such certificates be regarded as advisory only, with the airlines' own medical representatives ultimately being responsible for deciding whether a passenger is permitted to fly. This is because clinicians who are not specialized in aviation medicine are unlikely to be fully familiar with either the particular medical concerns of air travel or the medical capacities onboard, and medical clearance procedures differ significantly between airlines and internationally. [2]
  • While this section outlines key areas to consider when assessing fitness to fly, concerns should always be discussed with the airline's designated medical representatives.

General considerations

  • Preexisting medical conditions: potential inflight deterioration; limited inflight emergency medical resources (see “Inflight medical events”)
  • Medications: dosage, timing, potential disruptive effects of travel
    • Patients should be advised to carry medications and basic medical records (e.g., medication schedules) in their hand luggage.
  • Need for assistance or special services such as wheelchairs, stretchers, lifting services, special meals, special seating, early boarding, and supplemental oxygen
  • Public health concerns (e.g., communicable diseases, vaccination status)

Relevant systems and conditions

System-based approach to preflight screening [1][2][3][4]
System Key conditions/events Pathophysiology Investigations and patient advice
  • At a relative cabin altitude of 8,000 feet, the decreased barometric pressure results in a PaO2 of 60–70 mm Hg and an SaO2 of ∼ 90%, even in healthy travelers.
  • Individuals with a low baseline PaO2 can develop hypoxemia.
  • Contraindications to air travel:
    • Untreated pneumothorax or within 2 weeks of drainage and full expansion
    • Active or contagious respiratory infections
    • Labile asthma or recent hospitalization with asthma
  • Perform an ABG for patients with symptomatic pulmonary conditions:
    • PaO2 > 70 mm Hg at sea level should allow the patient to fly without O2 supplementation.
    • Patients with stable conditions who do require supplemental O2 usually cannot bring their own, but most airlines will supply O2 at 2–4 L/min for a fee. [1]
  • Obstructive lung disease: advise patients to carry their inhalers and an emergency course of oral steroids in hand baggage
Communicable diseases
  • Available data is limited, but risk of transmission appears highly variable and is affected by cabin air recirculation and filters. [5]
  • Contraindications to air travel:
    • Any active or contagious infection that could be transmitted to other passengers (advise against travel until the end of the infectious period)
    • For tuberculosis, a minimum of 2 weeks of treatment with a documented response is required before air travel can be permitted. [2]
  • Increased risk of thrombosis for travel > 4 hours [1]
  • Patients with anemia are more vulnerable to the hypoxemic stress of air travel.
  • Time zone changes and associated meal time changes necessitate medication adjustments.
  • Insulin pumps may increase delivery slightly on the ascent as ambient pressure drops. [4]
  • Advise patients to carry twice the amount of all necessary medications and equipment; at least half of these supplies should be carried in hand luggage.
  • A physician's letter that contains information regarding the diagnosis, drug dosages, and if applicable the need to travel with needles and syringes is advisable.
  • There are algorithms for insulin adjustment in eastward and westward travel, but self-monitoring of blood glucose using a glucometer may be more simple for the patient.
  • Air travel may be contraindicated if the patient's behavior is unpredictable or disruptive.
  • Close liaison between treating physician and airline
  • Consider traveling with a patient escort or companion.
  • Recent open abdominal surgery
  • Recent surgeries involving significant blood loss
  • Pneumonectomy or lobectomy with decreased pulmonary reserve
  • Neurosurgical patients
  • Orthopedic patients with plaster casts
  • Postoperative patients have increased O2 consumption and may be more vulnerable to the hypoxemic stress of air travel.
  • Postoperative anemia has increased as transfusion has become less routine ; cases of severe anemia may necessitate supplemental oxygen.
  • Intestinal gas from a postoperative relative ileus expands at altitude and can cause bleeding or even perforation.
  • Trapped intracranial gas also expands at altitude and will increase intracranial pressure.
  • At a minimum, advise against air travel within 1–2 weeks of abdominal surgery and within 1 week of neurosurgery.
  • Consider the need for supplemental O2 in postoperative anemia with Hb < 8.5 g/dL. [3]
  • Most airlines prohibit flying within 24–48 hours of plaster cast application because of the increased risk of tissue swelling and compartment syndrome in this period. [2]
  • Retinal detachment surgery may involve intraocular gas injections. Remnant gas expands at altitude and can cause visual loss.
  • Contraindications to air travel:
    • Intraocular injection of perfluoropropane within 6 weeks
    • Intraocular injection of sulfur hexafluoride within 2 weeks
    • Other intraocular procedures or penetrating eye injuries within 1 week
  • Contact lens wearers, or patients with dry eye conditions such as keratoconjunctivitis sicca, may find the dry cabin atmosphere unpleasant. Advise the use of lubricating eye drops.
  • Cabin environments are not known to be hazardous to pregnancy.
  • Inflight delivery is a concern.
  • Scuba diving
  • Recommended intervals prior to flying: [3]
    • After a single dive: 12 hours
    • After multiple dives or dives with decompression stops: 24 hours
    • After treatment for decompression illness: 72 hours

Inflight medical eventstoggle arrow icon

Although inflight medical events (IFMEs) are relatively rare, there is a realistic chance that clinicians will have to provide onboard medical assistance within their lifetime. IFMEs pose a special challenge because of limited patient information and medical equipment, confined space, language barriers, and legal uncertainties.

Epidemiology [6][7]

Etiology [6][8]

Risk factors in the cabin environment for an IFME

Most common IFMEs [6]

General considerations for IFME management

Ground-based medical support [6]

  • Many airlines work with ground-based physicians who are trained in aviation and emergency medicine. These physicians are contacted via radio or satellite telephone by the pilot and can provide guidance to medical volunteers or cabin crew in case of IFMEs.

Procedure [8]

After the flight crew requests medical assistance:

  1. Assess your capability of helping the patient. Did you consume alcoholic beverages or take medications that might impair your judgment?
  2. Introduce yourself to the cabin crew and describe your medical qualifications.
    • Some airlines require proof of medical license.
  3. Ask for a medical emergency kit.
  4. Introduce yourself to the patient in a calm manner.
  5. Obtain the patient’s consent if possible; crew members can serve as witnesses.
    • Communication may be difficult due to language barriers. If a language interpreter is needed, consider patient privacy.
  6. Take patient history, perform a focused physical examination, and obtain vital signs.
    • Remember a pulse oximeter reading of ∼ 90% is normal at standard cabin air pressure.
    • If a loud cabin environment makes auscultation for manual BP measurement impossible, confirm systolic BP by palpating the radial artery during cuff deflation or watching for return of the pulse oximeter waveform.
  7. Administer treatments (in coordination with ground-based medical support if available and within your expertise).
    • If the necessary medication is not included in the airplane emergency kit, ask the patient if they have their own medications. Consider asking other passengers if the patient does not have medications with them.
  8. Ensure proper positioning of the patient: seated if possible, but if there is impaired consciousness or the condition is potentially life-threatening, supine in a more spacious area such as the kitchen or lavatory area, to allow any necessary resuscitative measures
  9. Discuss your assessment with the pilot and ground-based medical support and recommend aircraft diversion if the patient is critically unwell.
  10. Provide care until the patient is stabilized or you are able to transfer care to other medical personnel.
  11. Document your medical assistance (some airlines provide standardized forms).

A pulse oximeter reading of ∼ 90% is normal at standard cabin air pressure.

Auscultation will likely be more difficult due to the noise and vibration of the aircraft.

Aircraft diversion [6]

The pilot makes the ultimate decision to divert the aircraft. All other personnel involved, including ground-based physicians, flight staff, and medical volunteers onboard, act in a purely advisory capacity. Volunteer care providers are not usually knowledgeable about many of the factors involved in deciding aircraft diversion (e.g., medical capabilities of the nearest airports, operational risks of landing at particular sites).

Contents of medical emergency kits [6]

All US airlines must have an emergency kit on board that fulfills the minimum requirements of the Federal Aviation Administration (FAA). These emergency kits include:

  • Equipment for basic medical assessment, hemorrhage control, and intravenous fluid and medication administration
  • Medications to treat common medical conditions, including severe symptoms (e.g., mild pain, allergic reactions, bronchoconstriction, hypoglycemia, dehydration, certain cardiac conditions)
  • An automated external defibrillator
  • Some airlines provide a wider selection of devices and medications. Common supplementary devices and medications include a glucometer, urinary catheter, antiemetic and anticonvulsant medications, and an expanded selection of analgesic and cardiac medications.
  • Oxygen bottles available on commercial aircraft usually provide an oxygen flow of 2 L/min (low) or 4 L/min (high). Oxygen supplies may not be sufficient for the full duration of the flight, even for a single passenger.
FAA-mandated medical emergency kit
Equipment Medications

Pulse oximetry equipment is not mandated by the FAA!

Legal considerations [6][8][9]

  • In general, the country under which the airline operates has jurisdiction.
  • In the US, Canada, England, and Singapore, physicians are not legally bound to provide medical assistance unless there is a preexisting physician-patient relationship. In contrast, Australia and many European, Middle Eastern, and Asian countries have laws that require physicians to help in case of medical emergencies.
  • Legal liability:
    • In the United States, clinicians providing medical assistance are protected from legal liability by the Aviation Medical Assistance Act (i.e., “Good Samaritan” law), except in cases of gross negligence or willful misconduct.
    • Some international airlines provide “declarations of assumptions of legal liability” to protect medical volunteers from legal action.
    • In practice, the risk of legal action after inflight medical assistance is minimal.
  • Clinicians who provide medical assistance should not be under the influence of alcohol, illicit drugs, or sedating medications.
  • Basic first aid and CPR/AED training for the cabin crew is required in the US.

In practice, the risk of legal action after inflight medical assistance is minimal.

Space medicinetoggle arrow icon

Common complications of space travel [10] [11]
System Conditions





  • Average bone loss of 1–2% per month
  • Loss of muscle mass and strength, particularly in the lower extremities
  • Regular resistance and cardiovascular training during spaceflight (e.g., treadmill, cycle ergometer, rower)
  • Adequate nutrition (e.g., vitamin D supplementation)
  • Post-spaceflight orthostatic intolerance
    • Before landing on earth, wearing an anti-G suit, which has inflatable parts in the lower extremities to resist blood pooling
    • A few days after return to earth, rehabilitation for cardiovascular adjustment
Immune system
  • Adequate nutrition during spaceflight
  • Regular bacterial testing of shuttle consumables and environments (e.g., room air)
  • Desynchronized stimuli to the brain coming from the vestibular, visual, and proprioceptive systems due to microgravity
  • Preflight adaptation training
  • Limiting head movements in the first couple of days in spaceflight
  • Use of transdermal dimenhydrinate patches during EVA (extravehicular activity) to prevent vomiting
  • Promethazine as indicated
  • Spaceflight-associated neuro-ocular syndrome
  • Mitigation treatments, such as exposure to artificial gravity systems, are being developed.
  • Preflight and postflight screenings for elevated intracranial pressure
  • Unusually short light-dark cycles (every 90 minutes) onboard the international space station (ISS) and heavy workload
  • Factors affecting sleep hygiene: noise, mechanical discomfort, temperature changes
  • Difficulty falling asleep
  • Performance and concentration decline due to nonrestorative sleep
  • Optimized sleep hygiene, including regular sleep schedule and exercise
  • Daily dose of supplementary melatonin
  • Increased number of stressors encountered in spaceflight:
    • Physical: microgravity, acceleration, radiation
    • Psychological: isolation, confinement, danger, monotony
    • Interpersonal: cultural differences, personality conflicts
  • Asthenization: an adjustment reaction
  • Fatigue, irritability, concentration decline, loss of appetite, psychosis
  • Asthenization: a syndrome experienced after long-term spaceflight involving fatigue, sleeping disorders, irritability, emotional lability, lack of appetite, difficulties with attention and concentration
Multisystem involvement
  • Large spikes in radiation due to solar flares can cause acute radiation injury
  • Increased background radiation unique to outer space (e.g., high-energy protons, alpha particles, high-atomic-number ions)
  • Preflight predictions of solar activity
  • Protective suits during EVAs

Referencestoggle arrow icon

  1. Bettes TN, McKenas DK. Medical advice for commercial air travelers.. Am Fam Physician. 1999; 60 (3): p.801-8, 810.
  2. $IATA Medical Manual Edition 12.
  3. Aerospace Medical Association Medical Guidelines Task Force.. Medical Guidelines for Airline Travel, 2nd ed.. Aviat Space Environ Med. 2003; 74 (5 Suppl): p.A1-19.
  4. Assessing fitness to fly. . Accessed: March 10, 2021.
  5. Mangili A, Gendreau MA. Transmission of infectious diseases during commercial air travel.. Lancet. 2005; 365 (9463): p.989-96.doi: 10.1016/S0140-6736(05)71089-8 . | Open in Read by QxMD
  6. Martin-Gill C, Doyle TJ, Yealy DM. In-Flight Medical Emergencies: A Review.. JAMA. 2018; 320 (24): p.2580-2590.doi: 10.1001/jama.2018.19842 . | Open in Read by QxMD
  7. Peterson DC, Martin-Gill C, Guyette FX, et al. Outcomes of medical emergencies on commercial airline flights.. N Engl J Med. 2013; 368 (22): p.2075-83.doi: 10.1056/NEJMoa1212052 . | Open in Read by QxMD
  8. Graf J, Stüben U, Pump S. In-flight medical emergencies.. Deutsches Ärzteblatt International. 2012; 109 (37): p.591-601; quiz 602.doi: 10.3238/arztebl.2012.0591 . | Open in Read by QxMD
  9. Nelson B. Medical emergencies in flight: Are doctors prepared to improvise?: Pathologists and other physicians may be called upon to volunteer during an in-flight emergency. Despite the challenges, new resources may help them rise to the occasion.. Cancer cytopathology. 2019; 127 (12): p.733-734.doi: 10.1002/cncy.22215 . | Open in Read by QxMD
  10. Guo JH, Qu WM, Chen SG, et al. Keeping the right time in space: importance of circadian clock and sleep for physiology and performance of astronauts.. Mil Med Res.. 2014; 1: p.23.doi: 10.1186/2054-9369-1-23 . | Open in Read by QxMD
  11. NASA Guidelines on Space Medicine. . Accessed: March 12, 2021.

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