Do we have access to an archive of some sort, were we can see lots of other images like that, that is not claimed to be special in any way. Doing extensive analysis on a single image includes too much guesswork in terms of what different planes and temperatures looks like and how exactly they will look like on different instruments.
So if we had 100 other similar pictures to compare with, it might be obvious if something is out of the ordinary - or just look like any other picture.
Lets say 100 normal airline jets, some fighterjets with afterburner, different kinds of ballons, birds, special weather conditions etc.
Would help a lot.