UFO (TV series)
A single season of 26 episodes (including the pilot) was filmed over the course of more than a year; a five-month production break was caused by the closure of MGM-British Studios in Borehamwood, where the show was initially made. Production then moved to Pinewood Studios in Buckinghamshire. "UFO" was first broadcast in the UK and Canada in 1970, and in US syndication over the next two years.
Ufology
The first official USAF investigations of UFOs were Project Sign (1947–1949) and its successor Project Grudge (1949). Several hundred sightings were examined, a majority of them having a mundane explanation. Some sightings were classified as credible but inexplicable, and in these cases the possibility of an advanced unknown aircraft could not be ruled out.
The initial memos of the project took the UFO question seriously. After surveying 16 early reports, Lt. Col. George D. Garrett estimated that the sightings were not imaginary or exaggerations of natural phenomena. Lt. General Nathan F. Twining expressed the same estimate in a letter to Brig. General Schulgen, and urged a concerted investigation by the Air Force and other government agencies. Twining's memo led to the formation of Project Sign at the end of 1947. In the summer of 1948, Sign's first intelligence estimate (Estimate of the Situation) concluded that some UFO reports were extraterrestrial in origin. The rejection of the estimate by USAF Chief of Staff Gen. Hoyt Vandenberg led to the dissolution of Sign and the formation of Project Grudge.