This date (July 29, 1952) we have been discussing whenthe Mayher film was (reportedly) taken is a famous date in UFO history. It is the date that General Samford told the assembled press that (a) there was nothing to fear and (b) it was all weather phenomena (and misidentifications and hoaxes)...or something like that.
This date is also important for a much less well known fact, a fact that was not known by anyone outside the FBI until the late spring of 1977 (when I got the FBI file). This fact is that Samford was "lying with clenched teeth.An FBI document dated July 29, 1952 reports that an FBI agent contacted AF intelligence (Samford's office) and was told, >among other things, that 2 - 3% of the sightings could not be explained and that "it is not entirely impossible that the objects sighted might possibly be ships from another planet." There is no way that Samford was not aware that some sightings couldn't be explained. But unexplained sightings introduce uncertainty as to whether or not there is a potential threat (contradicting a) above) and weather phenomena (and misidentifications and hoaxes) did not explain all sightings (contradicting (b) above). Had Samford stated to the press what AF intell told the FBI, the lid would have blown off (maybe!).
Here are two documents. The July 29 FBI doc about "interplanetary ships" and a second FBI document, from October, which indicates the impact of the Newhouse (Tremonton) film. It, again, mentions interplanetary ships.
Note that the FBI was like a black hole: information went in and nothing came out(until 1977).