Minnesota, October 1955October 1955

On the night of October 21, 1955, two fighter pilots from the 432nd Fighter-Interceptor Squadron based in Minnesota reported separate but seemingly connected sightings near Minneapolis.

The first sighting came from Lieutenant William F. Steck, a pilot flying near the city. He saw an oblong, glowing white object that made a sharp 90-degree turn. The sighting lasted only about two seconds, and Steck described it as moving very fast with no visible tail. Around the same time, Lieutenant Donald E. Chanau, flying nearby, picked up the object on his radar screen. On radar, it appeared oblong in shape and registered on the scope for between 15 and 20 seconds. The object was tracked at various ranges up to about 7 miles away. The radar controller at Kidston Ground Control Intercept Station reported that the target appeared to be traveling at around 1,200 miles per hour.

The Air Force's initial analysis noted two possible explanations. For the visual sighting, investigators suggested the sharp 90-degree turn might have been an optical illusion caused by Steck's own aircraft banking at the time of the brief sighting. Regarding the radar contact, the Air Force pointed to a very strong temperature inversion (a layer of warm air trapped between cooler layers) that existed in the atmosphere between 35,000 and 39,000 feet at the time. This type of atmospheric condition can create false radar signals through an effect called anomalous propagation. A secondary temperature inversion was also detected at lower altitude around 4,380 feet. The file indicates the case was evaluated as "unknown," though the stated conclusions lean toward natural explanations.

The full case file is reproduced below as held by the National Archives, comprising 21 pages of scanned records.