Lots of secret government files about the UFO sightings have been released to the public.
The government's received thousands of reports of UFO sightings since the end of World War II. Now the files about these have been released to the public, including the file about this unidentified flying object in Nottinghamshire. Can you see it above the building?
But not all of these reported sightings could actually be investigated - a lack of funds and more important jobs meant a proper study couldn't be done. Here's another pic - could it be a flying saucer? Or just something else in the sky?
Unfortunately not everyone has a camera with them! Here's a sketch of a UFO claimed to have been seen by a police sergeant in Lancashire in 1979. The government closed its UFO desk in 2009, but that doesn't stop people thinking they've seen UFOs!
Here's a photo of strange markings on the ground in Rendlesham Forest, Suffolk, in 1980. There were reports of strange lights being seen at the time.
Here are more pics from the same forest. Other reported sightings include lights above Glastonbury and the bizarre tale of "worm-shaped" UFOs "wriggling around in the sky" over East Dulwich in London in 2003. What do you think?