Yuma, ArizonaApril 1952

On April 17 and 18, 1952, military weather observers at Yuma Test Station in Arizona reported seeing a mysterious object streak across the sky. The witnesses were trained meteorologists stationed there as part of their regular duties. All observers agreed the object was unlike anything they had seen before, and none of them believed it was a weather balloon.

The sighting on April 17 happened between 1505 and 1510 hours (roughly 3:05 to 3:10 p.m.). A group of enlisted weather observers was on a training hike near the Colorado River, about three miles south of the test station, when one of them spotted the object directly overhead. All seven men saw it immediately. The object appeared flat and white, with a circular shape. It traveled across the sky in a generally smooth course at about 60 degrees azimuth (a compass direction roughly east-southeast). However, its path was not completely smooth or regular. A thin vapor trail accompanied the object intermittently, though it disappeared quickly and never stretched longer than one or two times the object's own diameter. The entire sighting lasted approximately seven seconds, from when the object appeared overhead until it vanished over the horizon. When held at arm's length, the object appeared to cover about one quarter inch of space.

The observers tried to judge the object's apparent size and speed. It traveled from directly overhead (zenith) to the horizon in roughly seven seconds, which would require substantial velocity. One of the men, a corporal with a degree in science and strong background in meteorology, estimated it would have been impossible to track the object with a theodolite (an optical instrument used by weather observers to measure angles and positions). The motion was too fast and too erratic.

On April 18, two of the weather observers reported another sighting while practicing with theodolites. This object also appeared flat and white with a circular shape, similar to the previous day's sighting, except no vapor trail was observed this time. The sighting lasted between five and ten seconds. Again, the object's movement was too erratic to track with instruments. The Air Force record card indicates the conclusion was "Unidentified."

The complete case file, comprising 11 pages as originally held by the National Archives, is reproduced below.