Project Blue Book Case #1163. On April 27, 1952, a bright object was observed over Yuma, Arizona — the third Blue Book unknown from this desert weapons testing hub (joining Cases #1310 from June 1952 and #2388 from February 1953). Yuma's extraordinary production of three unknowns placed it among the most prolific repeat-sighting locations in the Blue Book database.
The Army Proving Ground and Marine Corps Air Station made Yuma's airspace among the most heavily used military test areas in the country. The desert's crystal-clear atmosphere and unlimited visibility ensured that objects were seen clearly and that atmospheric misidentifications were minimized.
April 1952 was in the early buildup phase. The case was classified "Unknown."