UFOS at close sight: the unknowns of project Blue Book
Submitted: Tue Oct 12 2004
CT: Project Bluebook: UFOS at close sight: the unknowns of project Blue Book
Detailed Traffic Statistic From Alexa
Blue Book, the final more or less public U.S. Air Force UFO investigation took over from Project Grudge in 1952 and lasted until December 1969. By this time, almost 13,000 sighting reports had been collected by all three projects combined. Approximately 600-700 cases remained unexplained (depending on which Air Force statistics are accepted).