Project 10073 Record Card — Sighting of Unidentified Object, Hastings, Minnesota, 12 December 1951

On 12 December 1951, at approximately 1550 CST, Captain Donald K. Slayton of the 133rd Fighter-Interceptor Wing was conducting a test flight in an F-51 aircraft near Hastings, Minnesota. While cruising at 10,000 feet, Captain Slayton observed an unidentified object approximately one mile away and 1,000 feet below his left wing tip. Initially, the object resembled a kite, but the pilot noted that a kite would not typically be found at that altitude. Upon closer observation, the object appeared to be a round, white or silver disc, 18 inches to 2 feet in diameter. The object exhibited an illusion of spinning, which the pilot initially attributed to light diffusion. As the encounter progressed, the pilot observed the object perform a 180-degree left turn, followed by a 270-degree left turn, during which it appeared to gain speed rapidly. The pilot estimated the object's speed to be between 380 and 400 mph. At one point, the pilot perceived the object as two distinct discs approximately one foot apart. Despite the pilot's attempts to close in on the object, he lost sight of it when he turned his aircraft for further observation. The report, prepared by Major Gerhard P. Kaske, notes that the pilot concluded the object was not simply floating in space but was actively maneuvering. Despite these observations, the official evaluation recorded on the Project 10073 record card categorized the incident as a balloon.