This is a great book to share with young toddlers -- talks about all the things you are likely to see/do en route to getting on a plane. We did a lot of the stressing of "putting on your seatbelt" prior to first rides in my kid's own seat:
Also, has your kid discovered stickers yet? We used to take sticker books *everywhere* -- he was a huge fan, and could sit with one for 20-30 minutes.