This post gets a thumbs-up from me. The US Government has definitely used the UFO legend for disinformation purposes. And it serves another purpose too, because (in the eyes of the general public) it discredits everyone who believes UFOs are piloted by extraterrestrials.
"Exhibit A" for the use of the UFO legend as disinformation has to be the case of Paul Bennewitz, who the USAF eventually drove into a nervous breakdown by feeding him lies about visitors from outer space.
The various UFO investigations carried out for US defence bodies -- from Project Blue Book onwards -- have all been inconclusive. Eventually, defence chiefs just stopped worrying about the phenomenon, since it didn't appear to be a threat. But they found they were able to capitalise on the widespread public fascination with things seen in the sky, and they have milked that potential for all it is worth.
RE: Debunked: Governments fake aliens