I'm not sure on this one, and the pic is a bit small to examine closely. I see what is meant by the tree line, but this might just be coincidence. I remember reading about a Hunter being flown through a hangar, but I understood this to be a 'J' Type hangar, or a similar large hangar. I also vaguely recall seeing a photo of the real event, which might or might not have been similar to this one.
I don't think it's been 'Photoshopped', but it may be montage, or a re-touched version of the original, or possibly a 'dodged' reconstruction of the actual event.