I can't stand people talking to me just to make small talk. Of course the hello's are no big deal and if there is a meaning to the conversation I do not mind. But to small talk just to pass time really bothers me.
It's not that I want to be unsocial and I am miserable in life, but like a couple others mentioned, being on an airplane is my getaway from the world...where email and cell phones don't work. I really love just enjoying some music or reading a book without worrying about the weather or talking about someone's grandkids.