A easy way to learn how to fly the planes is to do it in the Editor. Find a map with lots of room. Once you have a soldier in the plane take DC, the arrow keys control the plane(ver. 1.02). "Up Arrow" is the throttle on the ground, just get the plane moving then hit the "spacebar", then "downarrow". Once in the air "uparrow"(descends), "downarrow"(climbs), left and right arrows (left and right). The spacebar lowers the landing gear. W,A,S,D, for newer versions.
Here's what's possible,