New documents have just been released by Britain's ministry of defense. The 209 files and approximately 52,000 pages released by The National Archives of Britain on Friday included reports from the public on strange lights and even alien abductions. It is the final set of UFO files in a series that the National Archives has released periodically.

Britain decided to shut down its public UFO hotline in 2009 because it produced "no defense benefit" and no evidence of extra-terrestrial beings in more than 50 years.

Released along with the reports of lights and alien encounters was a sprawling 4,300-page file describing strange sights over Stonehenge and Parliament.

One key document explains why the ministry suddenly shut down its UFO hotline in December 2009. A briefing prepared for then-defense minister Bob Ainsworthy by the RAF Air Command one month earlier had recommended that Britain's ministry of defense "should seek to reduce very significantly the UFO task which is consuming increasing resources, but produces no valuable defense output."

The briefing also said that in more than 50 years, "no UFO sighting reported to [MoD] has ever revealed anything to suggest an extra-terrestrial presence or military threat to the UK" and "there is no defense benefit in [MoD] recording, collating, analyzing or investigating UFO sightings."

The documents show that from 2000 to 2007, the ministry received on average 150 UFO sightings annually, increasing to 643 in 2009. Due to the proliferation of camera phones, the number of UFO reports in Britain doubled in 2008, up to 208 for that year. Britain's ministry of defense says sightings were especially dense during summer months, when people were more likely to be outdoors. The outpouring of reports made the workload "unmanageable."

"That really did put a strain on the resources that the MoD had committed to this subject, and really led up to their decision to finally pull the plug on Britain's X-Files, simply because they just didn't have the resources to investigate these sightings, or to look at them in any detail," said David Clarke, a UFO historian who reviewed the latest files in a YouTube video. "So they just tended to be filed away."

That is exactly what happened to the Stonehenge sighing. In January 2009, the ministry received several photographs that showed a speck in the sky over the stone monument. "I didn't see anything in the sky at the time, because I was focusing upon the stones," the witness wrote in an archived email, "Upon uploading them to my computer, though, I spotted the discoid shapes in the background. ... I'm sure you get this kind of thing every day! However, I'm very fond of my UFOs so needed to share them!" The ministry replied, saying that it doesn't try to identify the source of UFO sightings "unless there is evidence of a potential threat to the United Kingdom." 

Other reports include: A man claiming a UFO had abducted his dog, car, and tent while camping with friends in 2007; a letter from a child in school asking for the truth about UFOs after she had seen some strange lights; and a woman in Dorset claiming that she saw "a bright white fireball" that entered her house through her kitchen window.