Military vs. UFOs: The team examine incidents of alleged conflicts between the US Air Force and the RAF, and asking whether these encounters have been covered up. (S1, ep 11)

Area 52: Area 51 is considered the ultimate top secret facility, but there is another military site, known as Area 52, where strange phenomena have been witnessed for 10 years. (S3, ep 10)

Giant UFOs: The team probes some of the largest sightings of alleged UFOs ever recorded over the English Channel, including two eerie objects spotted by pilots in 2007. (S2, ep 10)

The NASA Files: The team analyses incredible NASA footage of reported UFOs, and interviews former NASA employees who allegedly witnessed cover ups first hand. (S1, ep 10)

The Silencers: UFOs are the biggest mystery of our time and somebody - or something - seems determined to keep it that way. (S3, ep 9)

UFO Storm: In 2008, the UK's Ministry of Defence released decades' worth of classified UFO files to the public. One month later, UFO hysteria ripped through the country. (S2, ep 9)

Vortexes: The team travels to Sedona, Arizona, long known for strange phenomena, to interview witnesses to unexplained sightings of lights and objects in the skies. (S1, ep 9)

Underwater Area 51: The team investigate the highly secretive underwater testing facility AUTEC, said to be used by the US Navy for weapons testing and underwater research. (S3, ep 8)

Alien Fallout: After seeing an odd flying object in 1980, a woman was hospitalised as she lost clumps of hair and skin. The team reopens her potential 'alien effects' case. (S2, ep 8)

UFO Dogfights: The team examines a declassified US Department of Defense report which analyses an alleged encounter between a fighter pilot and a UFO. (S1, ep 8)