You have just been struck by the dreaded .
If you’ve ever stepped off a red-eye feeling like your head is stuffed with cotton balls, you know how annoying—and sometimes painful—this can be. But why does it happen, and more importantly, how do you make it stop? It isn't a cold (though that makes it worse). It's physics.
Ask the flight attendant for hot water with lemon or a hot tea. The steam rising into your face helps loosen the mucus in your nasal passages, and the act of swallowing helps the mechanics.