Amateur historian John Greenewald has spent nearly two decades requesting declassified information from the US government regarding UFOs.
Recently, he posted more than 100,000 pages of documents on the US Air Force’s internal UFO investigations to the internet. Here are the top five things to know from the open files of Project Blue Book.
1. Project Blue Book had a sizeable mission
The origins of the ambitious project can be traced to June 1947, UFO researcher Alejandro Rojas tells the BBC.
The editor of Open Minds magazine says a well-respected businessman and pilot, Kenneth Arnold, was flying over Washington state when he witnessed several unidentified flying objects.
Arnold later described the crafts as “skipping like saucers”, which the media adopted and took to calling flying saucers.
This high-profile incident – along with several others, including a rumoured UFO landing in Roswell, New Mexico, the same year – led the Air Force to launch an investigative body.