My 3 year old son loves flying in the back of my arrow - he sits in the car seat and looks out of the window, without saying very much at all. I bought some junior ear defenders as I suspect that if I gave him a headset with a live mike, I'd never get him to shut up....
He used to sleep more than he does now in the aircraft.
My eleven year old daughter, by contrast, is far more interested in ponies, and is quite disinterested in aircraft. She thinks that it's no different to sitting in the car...if only she knew!