Flight controls are excellent in the game, apart from the random wobbles (that I guess are supposed to be turbulence). Planes are the same as they've always been, though more responsive, and helicopters are better than ever. They have a learning curve, though, and if you come in with your GTA IV muscle memory you'll need a lot of practise. V's choppers are faster and more manoeuvrable than any other GTA's, but the controls are extremely sensitive. Fly around for a few hours and you'll be swooping under bridges and threading between buildings like a champ.
I'm finding it hard to save planes at Trevor's airfield in Sandy Shores, though. I have the Duster saved there, and it respawns every time I come back, but I haven't been able to replace it with anything. The helipad works just fine, if a bit cumbersome; I fly a new chopper to the airfield, move the spawned chopper off the helipad, land the new one on it and it's saved for good. With planes, though, I move the Duster out of the hangar, taxi the new plane in, fly off for a while and come back to find the Duster back again. Does the hangar have a 'Press right on the D-pad to select vehicle' prompt like the helipad does?