Minneapolis, MinnesotaOctober 1953

Three research engineers employed by General Mills Aeronautical Laboratories in Minneapolis observed an unidentified object on October 15, 1953, while tracking a weather balloon over St. Paul. The sighting occurred between 1010 and 1015 CST (10:10 to 10:15 a.m.) from the roof of their laboratory at 2003 East Hennepin Avenue. The object was first spotted as a comet-like smoke or vapor trail heading south in horizontal flight, passing below the sun which was at an elevation of about 25 degrees above the horizon. The object itself was not visible to the naked eye initially, only detectable by its trail.

The object moved across the sky at a rate of 10 degrees in 9 seconds. Assuming an altitude of 40,000 feet, this represented a speed of approximately 900 miles per hour. After about 10 seconds of horizontal flight, the object appeared to enter a steep vertical dive lasting 10 to 15 seconds. During the dive, the object became visible several times, appearing to glow or reflect sunlight. The smoke trails ceased as the object leveled off. For a brief moment before disappearing, it appeared as a grey mass through the theodolite (a precision surveying instrument used to track the balloon). The object then vanished in a quick flash reminiscent of light reflecting off a mirror. Throughout the entire observation, no sound was detected.

The three observers were credible witnesses with extensive engineering backgrounds. One was a former pilot and meteorological engineer, another a private pilot with two years of post-graduate work in supersonic aerodynamics, and the third a development engineer. All three noted that while a jet aircraft might explain some aspects of the sighting, several features were puzzling. The speed exceeded what was normally observed for aircraft, a vertical dive of that severity would be extremely dangerous or suicidal, no jet engine sound was heard despite the apparent proximity, and vapor trails do not ordinarily form during vertical motion. Air Defense Command records indicated two F-86 jets were in the area south and west of Minneapolis at approximately the same time, but the Air Force concluded this information did not definitively correlate with the observation.

The Air Force evaluation listed the case as unknown. Complete documentation of this case, including observer questionnaires, weather analysis, and official reports, is reproduced below as held by the National Archives, comprising 40 pages.