The once-classified study, known as Project Blue Book, began in 1947 and compiled the details of official U.S. investigations into thousands of UFO reports. The project was terminated in 1969.
Of the 12,618 sightings considered under Blue Book, 701 have remained "unidentified.” Believers will suggest the possibility those sightings could have involved extraterrestrials, while others will label them as simply inconclusive.
The final conclusions of Project Blue Book were:
• No UFO reported, investigated and evaluated by the Air Force has ever given any indication of threat to our national security
• There has been no evidence submitted to or discovered by the Air Force that sightings categorized as "unidentified" represent technological developments or principles beyond the range of present-day scientific knowledge
• There has been no evidence indicating that sightings categorized as "unidentified" are extraterrestrial vehicles
Retired Air Force Colonel Robert Friend, who was the director of Project Blue Book from 1958 to 1963, said he thought the study should have been given to scientists following its closure.
"When I first took over the program, I wrote two staff studies, and in both instances, I recommended that [UFOs] be put into another agency which would give them full scientific investigations and analyses," Friend told the Huffington Post in 2012.
For years, the declassified documents resided on microfilm at the National Archives in Washington, D.C. UFO researchers, including TV producer and writer John Greenewald, spent years compiling the content and translated them into searchable content online.
Greenwald cautioned anyone looking for a declaration of the existence of alien lifeforms.
"If you're looking for a smoking gun, that's not necessarily going to be there in the sense that they're going to say aliens are here, they've been over our skies and here's an example. You're not going to find that,” Greenewald said.
Project Blue Book began after a pilot in Washington State said he saw several unidentified flying objects "skipping like saucers.” That same year, a rumored UFO crash-landed in Roswell, New Mexico
Formed in the years immediately following World War II, Project Blue Book was intended to stop the spread of public unease about a growing number of reported UFO sightings, the BBC reported.
"What's interesting about this is you start going through the Blue Book documents and you realize just how serious the government and the military took these records," Greenewald said.
Most of the cases investigated were deemed to be caused by weather balloons, swamp gases, meteorological events or even temperature inversions.
