UFO sightings over nuclear facilities trigger high alert responses - are they top-secret aircraft or something from another world?
An investigation into triangular-shaped UFOs seen in the 1980s and 90s - they might be the best evidence of extraterrestrial crafts?
Anti-aircraft guns blast the skies over Los Angeles when an unknown flying object is spotted by thousands in 1942 - is it from earth or could it be extra-terrestrial?
Roswell is the most famous UFO story in history and a piece of debris found at the desert crash site might shed new light on what really happened in 1947.
Well-documented sightings of UFOs by commercial airliner pilots may be proof of danger lurking in our skies.