To date, the firm conclusions of Project Blue Book are:
1. no unidentified flying object 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; and
3. there has been no evidence indicating that sightings categorized as
UNIDENTIFIED are extraterrestrial vehicles.
-- the summary of Project Blue Book, an Air Force study of UFOs from 1950
to 1965, as quoted by James Randi in Flim-Flam!
