Why flying is different from sitting in a car
Commercial aircraft cabins are pressurised, but not to sea level. At cruise the cabin is typically equivalent to somewhere around 1,800 to 2,400 metres of altitude. The proportion of oxygen in the air is unchanged, but the pressure driving it into the blood is lower, so a healthy passenger's blood oxygen saturation drops by a few percentage points.
For most people that is unnoticeable. For someone recovering from a heart attack, a chest injury, severe anaemia, a significant lung condition or a brain injury, that reduction can matter.
The second effect is gas expansion. As pressure falls, trapped gas expands by roughly a third. That is why a recent pneumothorax, gas introduced during eye or abdominal surgery, or a bowel obstruction can make flying genuinely dangerous rather than merely uncomfortable.
Third, flights mean prolonged immobility, dehydration, limited access to a patient in a window seat, and no medical facilities beyond a basic kit and whoever happens to be on board.
Discharge and fitness to fly are two separate questions
A hospital discharges a patient when they no longer need inpatient care. An airline clears a passenger when it is satisfied they can complete the flight safely without needing care that cannot be provided on board, and without diverting the aircraft.
Those are different tests. Someone can be perfectly safe at home with district nursing and still be unsuitable for eleven hours in an aircraft seat. The reverse also happens: a patient still in hospital may be entirely fit for a flight with an escort.
Common waiting periods after specific events
These are indicative only. Airlines set their own policies and the treating doctor's assessment of the individual always takes precedence. Where a condition has been stable and uncomplicated, shorter intervals are often accepted; where there were complications, longer.
| Event | Typically considered before flying | Key factor |
|---|---|---|
| Uncomplicated heart attack | Around 7–10 days, sometimes sooner if low risk and well | Stability, exercise tolerance, cardiology opinion |
| Coronary bypass or open chest surgery | Around 10–14 days | Residual air in the chest, wound healing |
| Stroke | Commonly 10–14 days, longer if unstable | Neurological stability, cause identified and treated |
| Pneumothorax (collapsed lung) | Usually 1–2 weeks after full radiological resolution | Confirmed resolution on imaging |
| Abdominal surgery | Around 10 days for open surgery, less for keyhole | Trapped gas, ileus, wound integrity |
| Eye surgery involving intraocular gas | Until the gas bubble has fully absorbed, can be weeks | Ophthalmologist confirmation |
| Fracture in a full plaster cast | Cast split or bivalved if applied within 24–48 hours | Swelling under an unsplit cast |
| Serious infection | Once treated, non-infectious and stable | Public health and other passengers |
Always check against the specific case
- These intervals reflect general aviation-medicine guidance, not a rule that applies to every patient.
- The treating doctor knows the complications; a table does not.
- Airlines may be stricter than guidance, and their decision is final for their own flights.
What the airline will ask for
For anything beyond a routine passenger, airlines use a standard medical information form completed by the treating doctor and reviewed by the airline's medical department. Submit it with the medical report, and allow several days, longer if oxygen or a stretcher is involved.
Possible outcomes are approval, approval with conditions (an escort, supplemental oxygen, a specific seat), deferral to a later date, or refusal. Clearance can also be withdrawn at the airport if the passenger appears less well than described.
- Oxygen in flight is never assumed. It must be requested, approved and supplied under the airline's rules.
- Needing help with toileting, feeding or medication generally triggers an escort requirement.
- Wheelchair assistance is separate from medical clearance and must be booked as well.
- A patient cleared by one airline may be refused by another on the same route.
If they are not cleared to fly yet
This is common and it is not a dead end. There are usually three ways forward.
Wait and travel later: a few more days of recovery can turn a refusal into a straightforward clearance, and this is often the cheapest and safest choice.
Travel with more support: an escort, or a stretcher installed in the cabin, changes what the airline will accept because the care burden no longer falls on cabin crew.
Travel on a dedicated air ambulance: no airline clearance is involved, because the aircraft is chartered and the medical environment is controlled by the medical team.
Practical advice for the flight itself
Where a patient is cleared for an ordinary flight, sensible preparation reduces the risk of problems.
- Carry all medication in hand luggage, in original packaging, with a doctor's letter and enough for delays.
- Book an aisle seat and, where relevant, a bulkhead row for space and access.
- Arrange wheelchair assistance in advance for every airport including transits.
- Keep hydrated, move the ankles regularly, and follow any clot-prevention advice from the treating team.
- Carry a copy of the discharge summary and a current medication list.
- Allow far more transit time than usual, tight connections are where things go wrong.