As early is late 1947, the USAF became interested in the subject of UFOs. This had a more to do with concern about Soviet aircraft possibly entering US airspace and less to do with alien spaceships. The USAF's experience in this field quickly made them unhappy dealing with the subject and they were glad to wash their hands of it. The following links provide my interpretation of the events that had transpired during the USAF's involvement wtih the subject.