UFO Book Chapter: 

“THE UFO EVIDENCE:
SECTION III: Air Force Observations”,

1964 (National Investigations Committee on Aerial Phenomena, Washington, D.C.)

Source: NICAP.org

Quote from the chapter:

“Before the issuance of Air Force Regulation 200-2 in 1953 (see extracts), a large number of significant UFO sightings by active Air Force personnel were made public.”

http://www.nicap.org/ufoe/section_3.htm

“AIR FORCE UFO SIGHTINGS” 
(date range: 29 August 1942-20 May 1961):

http://www.nicap.org/ufoe/ufoe19_20_21_22.htm

(abovetopsecret.com image)