Flying with a cold, an injury or a recent procedure

The points below about flying when unwell are ordered by how much difference they make, not by how often they get repeated.

Pressure is the mechanism

Cabin pressure in flight is lower than at sea level, so any gas trapped inside the body expands as the aircraft climbs. The middle ear is normally vented through a narrow tube that opens when you swallow, equalising pressure with the cabin around you.

A cold or an allergy swells the lining of that tube, so pressure cannot equalise and the eardrum is pushed outward. Descent is worse than climb, because the pressure difference then works in the direction the tube is least able to relieve. The same expansion applies to gas in the gut, in the sinuses, and in any cavity left by a recent procedure.

The ordinary cold

Flying with a heavy head cold is usually possible and frequently unpleasant, with the pain concentrated in the descent. Swallowing, yawning and chewing all open the tube briefly, which is why sweets were once handed round before landing.

Decongestants help some people, though they are not suitable for everyone and a pharmacist is the right person to ask. Children are affected more because their tubes are narrower and lie flatter, so they equalise pressure less easily. If pain is severe, or hearing does not return within a day or two, that is a reason to see a clinician rather than wait.

Recent procedures and medical clearance

Some procedures leave gas inside the body deliberately, and flying while it is still present can be genuinely dangerous. Airlines publish policies on how long after various procedures they will accept a passenger, and those policies differ between carriers.

For anything significant, a carrier may require a medical clearance form completed by a doctor before it will carry you. These forms take time to obtain, so the request should be made well before departure rather than at the airport on the day. This article cannot tell you whether you are fit to fly, and only your own clinician is in a position to answer that.

Immobility and circulation

Sitting still for long periods slows blood flow in the legs, which is the mechanism behind travel-related clotting risk. The risk rises with journey length and is not unique to aircraft, since long coach and rail journeys involve the same immobility. Moving the ankles, standing periodically and staying hydrated are the general measures usually suggested, and none of them costs anything.

On a long trip, people with particular risk factors are sometimes advised to take additional precautions, and that advice has to come from a doctor. Anyone with a history of clotting should raise a long flight with their own clinician rather than relying on general guidance.

Injuries, casts and mobility

A limb in a recent cast swells as pressure falls, which is why some carriers require a split cast for flights soon after injury. Crutches and mobility aids are normally carried free and can usually go to the aircraft door, but the process is worth arranging in advance.

Nine times in ten, extra legroom seats often sit at exits, where passengers must be able to assist an evacuation, so they can be unavailable to injured travellers. Requesting assistance is free and should be booked ahead, because staffing is planned from those requests rather than from arrivals. Wheelchair users should confirm how their own chair will be handled, since it usually travels in the hold and damage is not rare.

Airline and carrier policies differ, and they change without much notice.

Being ill on board

Cabin crew are trained in first aid, aircraft carry medical kits, and many operators can reach a doctor by radio during a flight. A diversion is a serious operational decision taken by the captain on advice, and it is not something a passenger requests. Telling crew early is better than telling them late, because their options narrow as the flight progresses towards its destination.

Nine times in ten, carrying a short written note of your conditions, medicines and allergies makes that conversation faster in any language. Travel cover generally excludes conditions you knew about and did not declare, which is a reason to declare rather than to hope.

Everything above, in order of what to do first

1. Pressure is the mechanism. Cabin pressure in flight is lower than at sea level, so any gas trapped inside the body expands as the aircraft climbs.
2. The ordinary cold. Flying with a heavy head cold is usually possible and frequently unpleasant, with the pain concentrated in the descent.
3. Recent procedures and medical clearance. Some procedures leave gas inside the body deliberately, and flying while it is still present can be genuinely dangerous.
4. Immobility and circulation. Sitting still for long periods slows blood flow in the legs, which is the mechanism behind travel-related clotting risk.
5. Injuries, casts and mobility. A limb in a recent cast swells as pressure falls, which is why some carriers require a split cast for flights soon after injury.
6. Being ill on board. Cabin crew are trained in first aid, aircraft carry medical kits, and many operators can reach a doctor by radio during a flight.

The takeaway

Cabin pressure expands trapped gas, so plan around that, and take anything clinical to a doctor rather than a search engine.

Pack for the trip you are actually taking, not the one in the photographs.