That's great! All I can suggest are light toys, colouring in, books to read her, and make full use of the in flight entertainment . How long is the flight? We've done Brisbane to Singapore, Singapore to London, London to Glasgow, Glasgow to Cork, Dublin to London, London to Singapore, Singapore to Sydney, Sydney to Brisbane, Brisbane to LA, and LA back to Brisbane. DD1 was under 2 though so we didn't get a seat.
Good grief. Are you insane???

I think the more you do it, the more kids are used to it... would you agree M? Ours weren't terribly good on the flight to Qld recently - but I reckon the older they get, the more the understand and get used to it... Who knows.