UFO records of US Air Force posted online: What was Project Blue Book, and do unexplained cases hint at cover-up?

Approximately 130,000 pages of UFO records belonging to the US Air Force have surfaced online. The declassified documents contain records of countless alleged UFO sightings over the past few decades.

There are numerous bizarre sightings, hundreds with no explanation, and they are all now available online thanks to UFO enthusiast John Greenewald, who posted the entire collection for the first time last week on his site The Black Vault, reports ABC News.

"There's absolutely something out there," he told ABC News. "The big question mark is: 'Have they come here?'"

According to the report, this entire collection was put together by Greenewald over a period of 20 years as he requested, collected and collated all these documents. These papers were declassified years ago but, until now, were not easily accessible to the public.

A bulk of Greenewald's document collection comprises cases from Project Blue Book - a series of investigations by the US Air Force that took place post the infamous alleged alien landing in Roswell, New Mexico, in July 1947. Reportedly, 12,618 sightings from 1947 to 1969 were investigated.

In 1969, the government announced it was no longer interested in pursuing the cases, saying that they had found "no evidence indicating that these sightings categorised as 'unidentified' are extraterrestrial vehicles."

But Greenewald said he never believed the US government's decision. "The military and the government want you to believe there's nothing to this topic," said Greenewald.

"When I look at the documentation, I'm a believer, based on that," he said. "I believe the documentation proves beyond a shadow of a doubt that there is a coverup going on."

"They really couldn't, at the end of the day, explain some of these more important cases," he added.

Click here to view the posted documents.