I fly a lot with my son (since he was 6 months old to now- an almost 6 year old) and I have found that the Little Einstein bath puppets have been some of the best entertaining toys ever. Of course, you have to not be too embarrased to put the puppet on and be the puppet voice. BUT, if you are okay with that, it truly will keep them entertained for a good chunk of time. AND, somehow, my son, at times, will listen better to the puppet more than he does mommy. :)
Also, I use the cheapy stickers (the book of 500 stickers you can purchase at Wal-Mart) and we put stickers on the back of the seat in front of us (of course, you take them back off when you are done). Your child can also decorate you with the stickers, as well. They love that.
And finally, the coloring books that come with the markers that only work on that special paper are awesome, as well.
Oh wait, the little bubbles that you sometimes receive at weddings works great, as well. I think you can pick up those at any party store. They do not make a mess because the bubbles are soooo tiny. And, of course, you can blow them down to the floor, not up in the air.
And finally, a travel size etch-a-sketch is wonderful.
Of course, munchies of all kinds is a must.
Most importantly, if you stay relaxed, it seems to help your child. Don't worry about other people. I have found that most people are very sweet and nice and helpful. As for the occasional turkeys, well, they will just have to deal with it.