I always try to be polite and considerate despite the situation. I believe it reaps far more rewards than being nasty does, even when I am very upset.

Years ago, I was flying up front thanks to platinum elite status and used "please" and "thank you" when communicating with a flight attendant. She turned around, facing the rest of the passengers, raised her voice and said something like, "Thank you for being so polite and considerate. It's not often we get passengers like you who have good manners." I was really surprised by her reaction. Looking back on it, I wonder if she was having a bad day or was really sick and tired of people feeling like they were entitled to treat her poorly because they weren't sitting in coach. Guess we'll never know...