E.G.
We have traveled by air a couple times with our daughter who is now 18 months. (One 3+ hr flight at 13 months & one 3 hr flight at 17 months). The DVD player worked wonders. We brought along several DVDs..and she'd watch most for anywhere from 10-20 minutes before getting bored. You can save space by not brining each case for the dvds. (We put about 5 or 6 into a plastic sleeve CD holder). Our daughter wasn't into coloring yet either...plus those crayons would go everywhere, right? We also packed LOTS of snacks in different snack baggies. Things we wouldn't always give her too (chocolate chips, goldfish, raisins,). You can of course bring an empty sippy cup and fill it once you go through security. We held off her nap for the entire day until the plane ride as well---so at take off she's was exhausted and DID end up taking an hour nap. (Though my arm fell asleep holding her...it was worth it!).
We had some of her favorite little books in the diaper bag too. Twice we got lucky and were seated in a row of 3 without a 3rd person! (So my husband and I could sit on either end and our daughter had her own seat in the middle!).
Good luck...the best part about the trip is when you finally land! :-)