Approximately 130,000 pages of files from an official 22-year Air Force UFO study, known as Project Blue Book, are finally available to the public for free online.
Project Blue Book began in 1947 under the name Project Sign. It evolved into Project Grudge, and then finally took the name Blue Book in 1952. After 22 years of official investigations of thousands of UFO reports, the project was terminated in 1969.
The summation:
The final conclusions of Project Blue Book were:
1) No UFO reported, investigated and evaluated by the Air Force has ever given any indication of threat to our national security
2) 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
3) There has been no evidence indicating that sightings categorized as "unidentified" are extraterrestrial vehicles.