I'm working on a faction of monsters for an upcoming project where, conceptually, they can all fly. But slapping a fly speed on a monster is often too powerful, particularly for low-level monsters. I instead had to do some thinking about what kinds of abilities give the theme of flying or aerial maneuverability, but are more limited in scope. In relative descending power order, here are some ideas:

* gains a fly speed; this is the most powerful option, especially if its fly speed is very fast
* can grant itself or another creature a fly speed for some limited amount of time per day (minutes or rounds)
* gains a fly speed for some limited amount of time per day (minutes or rounds)
* has a fly speed that is significantly slower than its land speed, which encourages it to remain near the ground
* can fly, but can only ascend at a 45 degree angle
* can fly whenever it moves, but must end each of its turns on solid ground or it falls
* can glide when falling (moving, say, 30 feet laterally for every 5 feet that it falls) and ascend only in updrafts
* can make a controlled fall of any distance (moving 5 feet laterally for every 5 feet it falls)
* can fall any distance without harm, and always lands on its feet
* can fall some specified distance without harm, and always lands on its feet