How about a portable DVD player? I just flew for the first time with my 3.5 year old son. I didn't have one, but did bring his Leapster with us, a travel size Magnadoodle and some books. And snacks, lots and lots of snacks, mostly things I don't let him have at home so it was a novelty. We also took several trips to the bathroom (we had an aisle and a middle seat so we didn't disturbe anyone). It got him some time to be moving a little and he was fascinated that the water in the toilets was blue, lol. I also tried and prepare him as much in advance about what to expect (that he'd have to wear a seatbelt, that he could use the Leapster but would have to wear headphones, etc.). Good luck!!!