Photographs could be manipulated WAY before digital technology; the techniques were different but the intention and effect was the same; deception.
Consider this; there were a bunch of photos of FAIRIES that were declared to be genuine back in the 20's.
So, I say UFO's might be U and F and O.
People see them; therefore they are a fact. They REALLY REALLY are an Unidentified Flying Object.
But that doesn't mean they are alien. Or anything else geee-whizzz, apart from a few occasions where people have 60'd the next generation of millitary aircraft in testing.
A weather ballon can be a UFO. Like the one at Roswell (wait for the true believer to scoff at my credulity... wait for me to ask for decent evidence... wait for them to blame their inability to prove their beliefs on me, or some conspiracy). Sun dogs are another frequent cause of UFO sightings.