Ancient Aliens is counting down ten of the most compelling UFO crashes that have been reported across the globe. From an acorn-shaped object that crashed in the woods of rural Pennsylvania, to a mysterious craft that washed ashore in Japan, and an earth-shaking impact in Britain that defies explanation, are these mysterious events proof that our planet has been visited by extraterrestrials?

Ancient Aliens is counting down ten of history's most compelling -- and covert -- projects that study the UFO phenomenon. From clandestine government organizations to agents that silence UFO witnesses and secret programs to reverse-engineer alien technology, are these mysterious projects evidence of contact with extraterrestrials?