When flying I usually try to wear something that's very comfortable. Mostly a long pair of trousers because it can get extremely cold during flights (especially night time flights!), a pair of sneakers and a top paired with a jacket I can easily remove or throw over according to what the temperature is like on board. And this is the outfit I wore during my flight to L.A. with Adidas Neo.
I usually wear the outfit that incorporates most of my clothes I want to bring along, during the day of my flight. Also I consider this as my number #1 trick. It sometimes collides with my "comfortably dressed for flight" rule. However this allows me to bring along half of my closet, even if it's just a three day trip.