South Ruislip, England, November 1950November 1950

On 10 November 1950, radar operators at Heston Airdrome near London picked up an unusual object on their SCR-584 radar screen (an air search radar set used to detect aircraft). The object appeared between 0859 and 1026 (roughly 9 a.m. to 10:30 a.m.). Radar contacts with the unidentified object lasted four separate times, with the longest lasting about one and a half minutes.

The radar operators tracked an object that gave returns similar to those of a B-29 bomber aircraft. However, the object's behavior was highly unusual. It traveled at speeds ranging from about 30 to over 1,000 miles per hour. More strikingly, it climbed from 13,000 feet to 30,000 feet in less than five seconds, and it made sharp, zigzagging turns that no conventional aircraft could perform. In one case, the object made 18 sharp turns of 100 degrees or more while traveling only 2,500 yards laterally. The object also descended to altitudes around 1,000 feet, where it would disappear into ground clutter (radar reflections from the terrain). Multiple experienced radar operators provided sworn statements describing what they observed on the radar scope.

The Air Force later concluded that the radar echoes were caused by abnormal weather conditions, specifically ice-laden clouds and heavy water-laden clouds. Officials noted that a similar pattern of unusual radar echoes had been detected at Wright-Patterson Air Force Base in Ohio on 8 March 1950, and that rapid changes in atmospheric conditions could account for the apparent movement and speed variations seen on the radar. No aircraft were scrambled to intercept the object due to poor weather conditions.

The full case file is reproduced below as held by the National Archives, comprising 26 pages.