Why Do My Ears Fill up When I Land in an Airplane?
The “fullness” in your ears when landing in an airplane is caused by unequal air pressure on the eardrum. The middle ear is connected to the throat by a narrow tube called the Eustachian tube.
It serves to keep equal pressure on both sides of the eardrum. When you descend quickly in an airplane, the pressure pushing in on the eardrum is greatly increased and causes discomfort until the pressure equalizes.
The tube corrects, this by letting air into the middle ear, and the “fullness” goes away. You can help equalize the pressure by swallowing several times.
The tube, however, is very narrow and can be blocked by inflammation or mucus due to a cold or other illness, and you won’t be able to equalize the pressure. Flying with a cold can be very painful during descent. The amount of discomfort each passenger experiences is going to vary widely, even from flight-to-flight.
Some other factors are individual physiology (some people will have bigger Eustachian tubes than others), illness, ethnicity/gender/gift-of-gab (some are more prone to talking than others, and talking can relieve the pressure), etc.