In 1948, the US government launched several inquiries into UFO sightings, which many believed were sparked by Cold War paranoia. In what became known as 'Project Blue Book,' more than 12,000 encounters with UFOs were looked into by the Air Force. Now, decades after the files were closed, the microfilms have been made available online for free – allowing anyone to re-examine the evidence. Scroll down for video Pictured is the staff of Project Blue Book, which recorded more than 12,000 encounters with UFOs. Sitting in the centre is Hector Quintanilla, the last chief officer of Project Blue Book
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The files relate to USAF investigations into UFO from 1947-1969
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They were conducted under 'Project Blue Book' which ended in 1970
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More than 700 cases remain unsolved, accounting for 5.5% of the files
The USAF says that @placeholder included 12,618 sightings reports, with 701 of which remained 'unidentified' – or around 5.5 per cent of the files.