Another option would be the get a 3DS if you fly fairly often. The old 3DS XLs are cheap these days and you get access to two great libraries in the DS and 3DS.
Just food for thought.
Battery life would be an issue though.
I notice most of the games mentioned in here are multi-platform/PC ports. Are there no "built for iPad" or "iPad only" games that anyone can recommend? There must be some unique gems out there that you can't play anywhere other than on tablet.