The one thought that occurred to me when I was taking the picture was "what exactly is the threshold for the DC-9". - so thats not too far from SetJet's issue.
As it happens, I've seen DC-9s do a handful of impressive climbs in 30 years of watching them that didn't seem too dissimilar (from whatever my vantage point was)..but anyway, my feet were planted on flat ground, it was the steepest ascent of the day, and all the images of other aircraft from that day were from the same spot and none seemed to come out in such a way as I would question if I was tilting them -either at all, or not siignificantly.
Having said that, discussions of illusions, cropping, DC-9 performance limits, level cameras etc. are not without value. But the suggestion/assumption that I took an image of a plane against the sky, with no reference point, and then deliberately rotated it to an implausible or impossible angle, and uploaded it, is incorrect.