3.4K views · 441 reactions | The history of UFO sightings in North America goes back nearly 80 years. Explore the timeline of some of the most famous sightings and listen to testimonials from witnesses and the experts who dedicate their careers into uncovering the mysteries behind them. Solve the unknown in the brand new series, UFOs: Investigating The Unknown, Tuesdays at 8pm on National Geographic UK. | National Geographic UK | Facebook

In 1989, Bob Lazar came forward with a remarkable story: the US government had hired him to work on the top-secret Papoose Lake/S4 facility, which is a few miles south of Groom Lake, at the Area 51 research centre known as "Dreamland," to reverse-engineer alien spaceships! | History In Pictures