Hi,
I travel long haul (26 hours) frequently and observed the following by other mothers:
-snacks
-toys/books
-Neverending walking up and down aircraft which is to be honest good for your circulation too
-if there are other children, playing with them
-taking him/her to 'meet' passengers (only willing ones though)
-rehydrate him/her a lot
-iPad with cartoons and child games ( children like to touch screen, even though they cant play the game yet)
For you:
-listening to music
-Red Bull/coke if you are fading
-an au pair/nanny if you can afford to take one with you?!
I personally oppose medication/forced sleep but can appreciate why some might resort to using it.
Hope you will manage without any remedies!