Altitude changes require the Eustachian tube to open frequently and widely enough to equalize the changes in pressure. The act of swallowing activates the muscle that opens the Eustachian tube. If you chew gum or let mints melt in your mouth, you will swallow more often, thus activating the muscle. Yawning is an even stronger activator of that muscle. During air travel avoid sleeping during descent, because you many not be swallowing often enough to keep up with the pressure changes.
Children are especially vulnerable because their Eustachian tubes are narrower than adults.
Babies cannot intentionally equalize or pop their ears, but may do so if they are sucking on a bottle or pacifier. Colds, sinus infections, and allergy attacks exaggerate air pressure problems, so it is best to postpone an airplane trip. Also, if you have recently undergone ear surgery, consult your surgeon on how soon you may safely fly. Despite the fact that hearing loss is the most common medical problem in the general population, there are only a few insurance carriers which cover part of the cost of hearing aids. This is an issue that SHHH National is working on.