Hi A., we just did an international airplane flite and local trains. I was nervous, but our 23 month old was great. What we did:
1. Try to plan flite around nap time.
2. Get to the airport early so that you can do everything not under stress. Then once you are checked in, walk around the airport a bit with your little ones. that way they will be tired on the plane. also, try to eat before you board..not a heavy meal tho.
3. onboard, we had some board books, some crayons and paper, and some small stuffed animals for imaginary play. he enjoyed looking around and out the windows.
4. He slept 2/3 time on the long plane ride and 1/4 time on the 4 hour train.
5. bring pillow case and blanket from home as it is more comfortable for them to fall asleep with familiar smells away from their familiar environment.
6. put some moisturizer on their cheeks in case there is excessive air conditioning.
Have fun. Hope this helps. Jilly