The easiest way? Straighten out a coathanger, attach it to the undeside of the plane/chopper (most have a convenient hole for this purpose, otherwise use a little tape), get someone to hold it up for you, and snap away. Then all you need to do is brush out the wire, and you're done. The more difficult way is to photograph the plane or chopper just sitting on the ground at the angle you want, and cut and paste onto a background with Photoshop. The only tip for this method is to make sure you match up the light source in your pic with the one in the background pic.