How is this in home, garden, or geometry? anyway, you can listen to music, play a video game on a ds or psp or gba, draw random stuff or draw whatever you see, talk to the stewardess or a chatty...
Sleeping is one option, but there is so much to choose from! You could play on any electronics you have, Color in coloring books, (even though most children do it, it`s still fun!) Watch an in flight...