Betty and I were talking about this last night. We finally agreed that the worst person to sit next to on a plane is someone who is afraid to fly or is a nervous/impatient flyer. Any small bump, small delay, peanuts instead of pretzels, whatever meal is served, unable to fit their "carry on" in the overhead bin, etc. causes either a series of "complaining", a the nervous "humph!", endless re positioning in their seat, or endless talking about all that is wrong with flying. Just shut up, read your book. It isn't that bad.
I know I'll probably be hated for saying this but it's true.