As part of a continuing effort to declassify government reports related to unidentified flying objects, the U.K.'s Ministry of Defense and The National Archives this week released about 8,500 pages of UFO-related documents, illustrations, letters, and parliamentary debates from 2000-2005.
Some of the files describe paranormal reports that turned out to be mere pranks; other stories of intergalactic proportions were ultimately found to have earthly explanations. But the British government said 5 percent of the cases remain unsolved.
"The official agenda is, I've been told, on both sides of the Atlantic, is that gradual disclosure has to be the way," Timothy Good, a UFO expert and believer, told ABC News' "Good Morning America."
In one account, a British man said he believed he may have been abducted by aliens from his London home in 1999. He said he saw an aircraft hovering over his house and then woke up the next morning to find he had lost a period of time.
The Ministry of Defense responded to his report saying that the aircraft was probably an "airship" and the so-called missing time period was likely the result of turning the clocks back for daylight savings time.
In another report, a retired Royal Air Force (RAF) officer described an "unusual atmospheric occurrence" in Sri Lanka in March 2004. He said he heard a clap of thunder and then saw a doughnut-shaped cloud in the sky that "did not rise but headed from the high atmosphere towards the earth."
Other files include civilian and military reports of "cone-shaped" objects and unusual flashing lights in the sky.
The newly release trove of documents also shows that, in the 1960s and '70s, the British government seriously considered a possible alien threat. The esteemed House of Lords even debated UFOs in January 1979.
When six "flying saucers" were discovered on the ground in southern England in 1967, military intelligence was mobilized to investigate. Police and the Royal Air Force were swamped with calls when people spotted six small metallic-looking saucers in a perfect line, and authorities.
"This was taken extremely seriously," said Nick Pope, a former U.K. government UFO investigator. "One of these was taken away for analysis, another was blown up in a controlled explosion."
Later it was revealed that the so-called flying saucers were nothing more than the a hoax created by engineering students.
But for true believers in the U.K. and around the world, these documents are just the beginning.
"I don't think the ministry has revealed everything by any means," said Good. "The facts are too disturbing for the majority of the populous. Some of them actually have bases and have had bases on planet Earth for maybe thousands of years."
Michael Luckman, a UFO supporter and director of the New York Center for Extraterrestrial Research, said he thinks it's time for the U.S. government to follow in the footsteps of its friends across the pond.
"We're absolutely on a fast-track to full disclosure," he said. "The U.S. should take a leadership role. Unfortunately, we've held back. ...This cover-up has gone on for more than 60 years."