What about change of direction?
What do you mean? Something like Maneuverability Classes? If so, as far as I can tell, there is no such thing in FC unless I missed something. I believe that was done on purpose, as Alex pointed out, to be more cinematic.
On a different note, I would see natural flyers being just as able to make course corrections as a human changing direction while walking. Its intuitive. If you really wanted to be more simulationist about it, you could either:
* Involve a DEX check to make 90-degree course changes at speeds above base.
* Use a Flying skill like Pathfinder does.
Just a few quick thoughts off the top of my head on it. Personally, I use the DEX check for extreme cases. Otherwise I don't really worry about it.