Our friends just flew out (and directly too) with their 18 month old child - very active! They said that he did cry a bit on the first flight but gave up on the second leg!
They found phenigan (I don't know if that's spelt right) helped (she was contemplating taking it too!!!
) and also a great idea they had was to take a cheap photo album (just a small plastic one) with photos of grandparents, cousins, aunties & uncles - it kept him quiet for hours just going through the pictures and pointing to different people & saying their names. They also brought a couple of toys on the plane.
When they got here - they brought his travel cot that he sleeps in during the day & his own bedding & he slept straight through from night one!!! (and managed to go through most of the day when they got here without sleeping much as it was all so exciting!)