Hey there, i just did a 15 hour flight with my 20 month old....as mentioned the dvd player was a god-send!!
i also bought a make bag and filled it with interesting things, "Tiger" in southside are full of bits that kids hav never seen b4 and keep them very interested.
The stickers idea is agreed defo...lotsa minutes spent putting stickers everywhere
I bought a mini sketch-a-sketch from Next which he loved.
magazines of his fave tv program are good with lots of pictures to colour and nearly always lots of stickers inside too!
Hope all goes well...dont forget the calpol, we ended up getting very sick on the way home and calpol was much needed
Hav a great holiday!