Milk the snake/Claw the beaver whatever applies to you. No I'm serious masterbating releases endorphines to make you feel relaxed. It's also illegal to do in public but there are ways to be secretive about it.
Maybe go in the bathroom before boarding.
Alternatively fall asleep. The above helps with that as well.
http://www.youtube.com/watch?v=F1gWECYYOSo
Please Watch/Share this video so it gets shown in Hollywood.