J.W.
If he will watch a dvd you MUST get a dvd player or use your lap top or whatever, a hand puppet, and a couple of "I-spy" books.
If you have never medicated your child with Benadryl to make him sleepy, don't make the day of the plane ride the first time. It can have the opposite effect. It works great for my 3 y/o, but makes my friend's dtr a hyperactive mess. Do a test run. Remember - pregnant women can take benadryl as a sleep aid. I understand about not giving them something they don't "need," but you and the other people on the plane will "need" it if he's tierd, but can't sleep.
Don't forget tylenol for ear pressure pain, if you don't use the benadryl.
Special snacks, something you know he will like, but save it "special" for the trip - a (low sugar) surprise!
Don't forget your prayers that the stars align and he cooperates - nothing is foolproof! Good luck - oh, and I've found if you ask to sit in the back where it is noisiest, if fits ensue, you won't bother as many people or get as many dirty looks - coming from someone who has done lots of traveling with a toddler, and gotten her fair share of dirty looks too! Have a safe trip.