The aircraft are just like normal locos, in that they are not free-flying, but instead run on invisible track. You lay the track wherever you want the aircraft to go and "fly" the plane along that invisible track.
With the features incorporated into vulcan's excellent series of aircraft, (more details here) you can make the planes act very realistically, using a clever piece of kit known as an Aircraft Control Trigger. All you need to know is the appropriate trigger setting for the thing you want done and the trigger does the rest.
Have fun flying, and enjoy the wide range that's now out there.