Often an argumentative topic... best I can do to explain it is copy and paste from the rejection reasons list:
The photos were of low esthetic qualities - bad angle, included window reflections (for shots taken through glass such as terminal windows), pictured just a part of an aircraft (with no motivation, like a special sticker, damage etc., for doing so), out of focus, distracting or obstructing objects in the foreground or similar (this is especially true for gate shots which are very difficult to get accepted due to their common nature and the large amount of ancilliary equipment which usually surrounds the aircraft) or did not picture an aircraft or anything sufficiently related to aviation at all. Finally, you might read this because your camera displays the date in the lower right corner of the image. If so, please disable that feature in the future.
I've had my fair share of badmotiv rejections I don't agree with... but then again, what IS
the motivation for us to go spend silly amounts of money on equipment to take photos of big mechanical birds?