Unidentified Flying Object

UFO was, during the 20th and 21st centuries, a human designation standing for Unidentified Flying Object. Many UFOs were believed by some of the general public, such as Eugene Jones and Maxwell Edison, to be alien spacecraft. Particularly in the 1950s and into the 1970s, the public often reported UFOs as flying saucers, crewed by "Martians".

Alien defence organisations such as UNIT and the Torchwood Institute and insiders like Henry van Statten knew that many UFOs did, as suspected, come from planets other than Earth.

References and appearances

 * UNIT noted frequent UFO activity centred around Tobias Vaughn's company, International Electromatics, and correctly suspected alien involvement. (TV: The Invasion)
 * The Tenth Doctor and Rose Tyler went undercover at Deffry Vale High School after Mickey Smith and locals of the borough first noticed UFO activity - "lights in the sky" - around the area, later shown to be of Krillitane origin. (TS: Tardisode 4, TV: School Reunion)
 * The Torchwood 3 briefly went on alert after UFO sightings in Cardiff airspace. They discovered it was only an excursion by members of the non-threatening Arcateenians. (TV: Cyberwoman)
 * Sarah Jane Smith investigated some UFO activity which later turned out to be caused by a Sontaran known as Kaagh. (TV: The Last Sontaran)