Here are two examples of fake UA175 photographs I quickly made in
Photoshop using Flight Simulator to generate the correct image of a Boeing 767.
It took about 1 hour to manufacture each image and they aren't particularly convincing,
but it does demonstrate that photographic forgery is achievable for the layman.
Please note the second image is deliberately showing a Boeing 767-300 unlike the
Boeing 767-200 below:
If this is what can be achieved by a novice Photoshop user in an evening then
imagine what a skilled team of professional forgers could achieve in a few days.