Why your ears pop on a plane

That full, muffled feeling on take-off and landing comes from a small tube between your ear and your throat. Here is what it does, and why landing is often worse.

Behind each eardrum is a small pocket of air, the middle ear. It holds the tiny bones that pass sound on to the inner ear, and the eardrum seals it off from the air outside.

Its only link to the outside is the Eustachian tube, a narrow channel that runs from the middle ear to the upper throat behind the nose. Most of the time the tube is closed. It opens briefly, most often when you swallow, and also when you yawn or chew.

The eardrum works best when the air pressure on both sides of it is the same. When the pressure outside changes and the middle ear hasn't caught up, the eardrum is pushed in or out. Sounds go dull, and the ear feels full or sore.

What happens on a flight

Airliners are pressurised, but not to the pressure at sea level. On commercial aircraft the cabin is kept at a pressure equal to an altitude of 8,000 feet (about 2,400 metres) or lower. So the cabin's pressure falls after take-off and rises again as the plane comes down.

On the way up, the air in your middle ear ends up at a higher pressure than the cabin's, and it tends to work its way out. On the way down, it is the other way round: the cabin's pressure climbs above the pressure in your ear, and the tube has to open to let air in. That doesn't always happen by itself, which is why the descent is often the uncomfortable part.

The pop is the moment the tube opens and the pressure evens out. That is why swallowing, yawning or chewing gum helps. Another way is to pinch your nose, close your mouth and gently try to breathe out through your nose, the Valsalva manoeuvre.

Some ears have a harder time. A cold or an allergy can swell and block the tube, so the pressure can't even out and the ear may ache during and after the flight. Children's tubes are shorter, narrower and lie flatter than adults', which is also why they get middle ear infections more easily.

Divers meet the same problem, only more sharply, since water pressure grows quickly with depth. For most flyers, though, it is a small thing: a tube that usually stays shut, asked to open a few times on the way down.