Really I realize that the fly skill is supposed to simply maneuverability categories, but I just don't see the point. Having to make random checks just to move is a bad idea, because it really slows the game down. And there are also a lot of complex rules to memorize. Most players just don't want to deal with that.
I advise just getting rid of the fly skill and going back to maneuverability categories but simplify them quite a bit. Forget about the turning radius, because quite simply, it's just too complicated to figure out in play and it makes even less sense in a game that doesn't even have facing rules.
Further just about every group I've ever played with has ignored the maneuverability class rules in the DMG, and I suspect that they'll ignore the fly skill checks as well. It's just too much work trying to figure out how fast you turn in midair and how many movement points you're spending to turn in place or what not. I don't think most groups even want to deal with that. It's clunky and it's cumbersome.
Here's what I would do. Three maneuverability categories: poor, average and good.
Poor: Your standard action becomes a move action while flying and thus you can only use it for move action related tasks. You cannot make attacks of opportunity while flying. While flying, your space (But not your size), doubles. So a 15x15 creature takes up a 30x30 space while flying. If it must squeeze to enter an area, then it crashes.
Average: You cannot make attacks of opportunity while flying. While flying, your space (But not your size) doubles. So a 15x15 creature takes up a 30x30 space while flying. If it must squeeze to enter an area, then it crashes.
Good: Your space while flying is equal to your normal space. If you enter an area where you must squeeze, then you crash.
And that's it. As far as crashing goes, you'd have basic damage assigned for hitting an object, and possibly have some feats that allow you to avert crashes (or maybe even keep the fly skill specifically for that purpose). So you might get scenes where a creature is flying in tight quarters and must make a check each round to avoid a crash if you want those sort of close quarters cinematic tense crash scenes.
I feel like my presented system is something that most groups are going to use, instead of the ignored maneuverability class rules, and I suspect the new PF flight rules, which are just too complex for most groups to care about.