Answer by Dragonlance

In the sky, the path is everywhere (only limited by the ground ...). So as fattie said, this is basically just LookAt. Maybe what you want is kinematic behavior, acting to the rules of middle school physics (an airplane will not rotate in a blink of an eye, it has to fly a curve etc.). Google for that stuff. This link could be helpful http://www.red3d.com/cwr/steer/gdc99/ The AI could be as simple as the desicion where to fly (directly to the player, wabpoint 1-2-3-4 or something). Harder it gets as soon as you want to have real dynamic flight physics or an AI that makes tactical descisions depending on the enemys and friends movements and situation. But most likely you will not need complex things. Simple things can look brilliant and be fun, or they even can be a special challange(just look at the WoW bosses and enemys, everything scripted with some randomness and some thresholds for dmg and aggro, no intelligence). Good luck and have fun!