P.G.
If she's used to traveling in her car seat, and you can afford to have her own seat on the plane, use the carseat if it's FAA approved. Since they're used to sitting in the seat, it may help. I googled the same subject and there are lots of hints out there as well. Part of the time she'll nap. Hopefully she'll look out the window a lot - shoot for the window seat if you can. Good luck!