I have flown with my DD quite a few times, for loooong trips too. The latest, form Phoenix to Guam (home) which is two 5-8 hr flights...sigh...
So here are my tips:
-Snacks!
Some you know for sure he will eat and some new funs ones he's never seen before. Always, lots of snacks, that will always keep them entertained, especially if they are finger ones.
-Baby carrier for sure!!
-Sticker/magnet books
I got a little magnet board book that you have a few magnets and stick them throughout the book, easy for little fingers not to crumple. Window cling type stickers are good too, especially if you get a window seat!
-Travel Bingo
http://www.amazon.com/Melissa-Doug-2.../dp/B000VNXSOQ
I found these at a toy store here in Guam. They are made by Melissa and Doug and all the kids love them. Even if they don't get the bingo part, they can learn what's behind each door and always love opening and closing the doors.
-Portable dvd player
Some may not agree, but this was a life saver for us. By far, the best thing I have bought for long trips on planes or in the car. If all else fails, you've gone through your snacks, all the new and old toys, they've had a nap and there is still 2 hours to go, bust out the dvd player!
If I think of more, I will come and update! Good luck!