Polarized means that the lens only allows light with a certain wave orientation through. They are good for reducing glare from reflection (off water/snow etc).
Cockpit windshields on a lot of aircraft (certainly airliners) are polarized, and if you wear polarized glasses and look through a polarized windshield, you may not be able to see anything outside at all... So, to answer your question, non-polarized are the type to get for flying!
Lancer