Hiya.
Does nobody understand that the ability to Fly is just that...the ability to Fly?
What is Fly? It's movement in the air. Let me say it a bit differently. It's movement in the air.
Aaracokra can fly...NOT hover. They can't "stop and fight from above". They have to be moving. You know...physics and lift and all that stuff. There are monsters that have Fly listed, and some that have Fly & Hover...so obviously there is a distinction (as there should be). They can't cast spells any more easily than a wizard walking down a hallway. They can't "fly up, cast a spell, then fly on"...as soon as they stop flying that pesky thing called *gravity* kicks in and they fall like a rock. Nor can they just "hover there" and shoot a missile weapon as they have to be moving.
Also, wingspan. An Aaracokra has a, what, 15' wingspan? Forget about flying anywhere other than wide open areas. Even in a 30'x50' room with a 20' ceiling. No room to maneuver or gain enough altitude.
I just don't get why people think a flying creature is so "overpowered". They aren't. Not in the least. Not in any way, shape or form, IME. Now, a magical flight that allows one to hover in place? That's different. That's quite powerful...not insurmountable, but definitely advantageous. But muscle powered "Flight" with no Hover capability? I just don't see it.
EDIT: And yes, I realise the vagueness of magical flight with this interpretation. On one hand, the Fly spell doesn't say you can hover at all...but the PHB listing for Flight specifically mentions "will fall...unless magical flight, such as the fly spell". I adjudicate this simply that with magical flight, you can move as slow as you want, but not stop [re: have a movement of 5']...but you are still moving. But, with our aaracokra friend, it's not magical...so no "movement of 5'".
^_^
Paul L. Ming