Fly-by attack has an advantage over Spring Attack and Ride-by Attack, because you can use it with *any* partial action. This means a dragon could fly on top of you, blast you with its breath weapon, and fly on. Or it could cast a spell. Or a beholder could use it to pop in and out of cover, blasting away with some eye-beams in the meantime. To balance out this advantage, it doesn't provide any protection from AoOs.
If you just want the ability to fly in, hit someone, and fly away, there's nothing in the description of Spring Attack that prevents it from being used with non-ground movement. There might be some trouble because it has harsher prerequisites.