The great advice I got from friends - that really worked - were these...
- make necklaces using mint dental floss, cheerios and, every so often, a fruit loop. My kid loves cheerios, loved to wear the necklace and was thrilled when she got a fruit loop, which she'd never had before
- stickers stickers stickers. Buy cheap ones and stick them on your kiddo. Mine spent lots of time taking them on and off, putting them on me, the seats, etc. It's fun to play together too - stickers on the nose, toes, etc. I actually keep them in the diaper bag all the time now and even whip them out, when needed, at the grocery store!
- a NEW toy. In my experience, noise is so muffled on the plane that something that makes a little noise isn't an issue.
Good luck!!