Flying would pretty much require a following camera perspective. First person would work, but why turn into a (hypothetical) dragon if you can not see yourself?

For flight you would need controls for speed, pitch (up/down - same controls as for forward/back on the ground) and yaw (left/right); roll should be handled automatically when turning, since there isn't really a need to independently rotate about the length of the dragon. Speed usually shouldn't need to be changed during an attack, but if you never need to change pitch (ie the angle of attack) fights would get kind of boring.

Between attack and flight controls, I think an automatic targeting system would be handy (without frequently pausing or turn based combat, I can not think of a way to fly and attack effectively if you have to select targets yourself). The closest opponent directly in front of you could be selected (maybe add a hotkey to cycle through available targets), allowing you to simply attack or left click an alternate target.

You can still click to move (fly to a point directly above the click), and ctrl-click to target the nearest opponent to the cursor, but that bypasses flight controls, and if your enemy has ranged weapons and decent aim, always flying in a straight line to attack isn't really a great idea.

It doesn't matter if you are flying yourself or on another creature for the purposes of the combat system, you still have to control both flight and attack.