My ds is different every flight. Usually, as long as we ration the junkfood & bring lots of books he is fine. We have flown into Newark, NJ (there was 6" of snow on the ground) with my son wearing only a bathing suit. (You see, he thought that all that blue he saw out the window was water.) That was our worst flight ever. The flight was delayed & the plane temperature was hot waiting in Fla. We just deal with each small problem as it comes & don't loose your cool. When you start getting those "looks," just tell those around you about autism. You'd be surprized how many people don't know.
My dd listens to Disney music with her preschool version of a walkman. She is sensitive to noise & this helps alot. I also bring books, & her favorite doll. I used to bring coloring books, but ds likes to eat crayons. I found little Disney books that are like paint with water books only they use a marker. My dd loves them & we don't have to worry about where the missing crayons are. (she hates to loose things)