In my opinion:
- Rarity of the aircraft....I consider a Cessna 175 at a sleepy little GA
airport much more interesting than another eurowhite A32X on final somewhere.
- Rarity of the angle
of the aircraft. For example, looking down on the aircraft from a control tower rather than a side-on shot from the terminal.
- Environment/surrounding details....this could involve anything from visible details of a fighter jet's underwing hard point at the extreme top of the photo, to a beautiful expanse of scenery behind the aircraft, to a lone ramper (recognizable or not) crouching near a baggage door in a severe snowstorm. Even placing the camera right on the ground and capturing some texture of the ramp would add some individuality and originality to the photo.
[Edited 2008-07-20 13:30:09]