You know your kiddo best.
What will it take to keep him quiet, calm, and not kicking the seat in front of him for 2.5-3 hours? A DVD? Music on an ipod? Playing Go Fish? Feeding him constantly? Sitting next to whom? And not next to whom?
What tricks work in restaurants and car rides?
My DD won't watch movies on airplanes. I think it's a function of the fact that she has a hard time hearing (even with headphones) and that she'd rather be crafting. (I bring scissors, tape, post-its, pens, and twistables on every flight. Post-its stick to anything!) I don't bring the DVD on planes any more.