We just returned yesterday from a plane trip with our 15-month-old. I had asked the same question on here and got some great ideas... some things that were the best for my son were a mini slinky (by far the thing that kept him entertained for the longest stretches of time), snacks and drinks. I had a bunch of other small toys that I think were good ideas, but didn't last him very long- but I think it all depends on your son. Other things I had were stickers, crayons, post-it notes, mini etch-a-sketch, matchbox cars, mini playdoh. Oh, I also gift-wrapped everything so it would take some extra time and seem exciting. I was all set with our portable DVD player, but there were not outlets on the plane, even though we were told by the airline that there were... if you have one with an external battery pack, that would be great, too. In addition to toys, we also did lots of little games like 'this little piggy', 'pat-a-cake', 'where is thumbkin' and good old tickling :) Have a great time, and good luck!