Duluth, MinnesotaMay 1955

On the night of May 13, 1955, two Air Force pilots flying an F-89D jet interceptor out of Duluth, Minnesota, spotted something unusual on their radar while on a routine training mission. The pilot and radar observer locked onto what their instruments showed as a target at 2:30 a.m. and tracked it for about 4 to 5 minutes.

The object began to the east of their position and moved in various directions. It started level with the interceptor, then climbed and descended as the pilots maneuvered their jet. What made the sighting remarkable to the aircrew was the target's reported speed. When the object moved away from them at the end of the encounter, the pilots and radar operator estimated it was traveling faster than 1,000 knots (about 1,150 miles per hour). The radar also recorded that the target came to a dead stop at one point before accelerating away.

The Air Force's technical experts examined the case and offered other explanations. They noted that the radar data could be consistent with an ordinary aircraft performing a tight turn. The Weapons Guidance Laboratory suggested that when the interceptor and target were flying parallel to each other, the target might have appeared stationary on the radar scope due to the geometry of the situation. The experts also pointed out that measuring speed from radar returns can be unreliable when the target is moving away, and that radar can sometimes jump lock and display false readings. Poor visibility of the elevation angle on the radar scope could also have affected the altitude estimates.

The file notes that weather in the area at the time was clear, with no unusual atmospheric conditions that might explain the sighting. The two pilots, Lieutenant Charles M. Middleton (pilot) and Lieutenant Donald G. Fisher (radar observer), were both rated as completely reliable observers. However, the Air Force's final evaluation appears in the file as simply "unknown." The full 9-page case file is reproduced below as held by the National Archives.