My first plane ride was when I was 8. I was (and still am) easily terrified...I have always feared the worse would happen and before the plane ride, I was not only afriad the plane would crash, but also worried that if we did make it down there, we'd be hit by a tornado.
lol.
Anyway, I had things like stuffed animals and teddies as well as items that my grandparents had given me like...notepads to write and draw in, makers, a deck of cards, snacks, activity books and the Walt Disney World Birnbaum for Kids lol.
The thing is, I got on that plane and found it to be VERY fun! I simply loved it and enjoyed looking out the window and observing how small everything looked. I didn't even use any of the things I brought because I was too engrossed in the flight...it WAS my first plan ride...
On the trip back, I did use the things I brought simply because I was bored lol, not because I was afraid.
I guess what I am trying to say here is you never quite know what to expect, your daughter might find it to be the best thing in the world!!
Now, years later, I am terrified of flying (but I have done it over 30 times lol).
Also, I remember I loved doing things with my parents. I loved playing cards with my dad and drawing with my mom.
I would suggest, for a gift, anything that gets her imagination flowing! You want her to think of everything else that isn't flying (if she is afraid). Maybe a book where she writes or draws a sort of trip "report". It is always fun for little kids to draw or write what he or she is doing, did do and hopes to do, especially for a first trip; especially if you are going to WDW (wherever you're going, she will most likely be very excited and a good way to release that excitement is through creativity and imagination!
Observe what she likes doing when she is bored...such as in a waiting room or anywhere that requires her to sit still and be on good behavior. By noticing what she finds interest in during these times will be a good clue as to what she may enjoy doing on a plane so a # amount of hours!