Cheyenne, WyomingMay 1955

On the night of May 22-23, 1955, two airmen stationed at Francis E. Warren Air Force Base near Cheyenne, Wyoming, reported seeing four unusual objects in the sky. The sighting occurred between 11:45 p.m. on May 22 and 12:30 a.m. on May 23, while the airmen were parked on U.S. Highway 85 about five miles south of Cheyenne. The objects appeared no larger than a baseball. Two were white, slender, and rectangular in shape, while the other two were dark and oval with a protruding top. The latter two objects glowed with an intermittent bluish-purple light. The airmen heard no sound and saw no trail or exhaust.

The objects moved together in a side-by-side formation. The two rectangular objects appeared about ten feet above the horizon and vanished after five or six seconds. The two oval objects were positioned much higher in the sky and remained visible for roughly five minutes. As they moved southward and upward, they brightened with their bluish-purple glow before disappearing from sight within approximately ten seconds. Weather conditions at the time were clear with unlimited visibility. A meteorologist from the U.S. Weather Bureau reported that no unusual atmospheric or astronomical conditions existed that could explain the sighting.

The Air Force investigated the report but was hindered by the delay in notification, which occurred four days after the sighting. An Office of Special Investigations (OSI) unit found no conclusive explanation. However, the official comments noted in the file state that "there is strong possibility that objects were res balloons release from California or Minnesota." The official evaluation of the case remained unidentified, though investigators suggested a balloon hypothesis. This 11-page case file is reproduced below as held by the National Archives.