36deg 40' N-130deg 50' E (FAR EAST), January 1951January 1951

In January 1951, a radar operator aboard an airborne patrol plane detected multiple high-speed targets near Guadalupe, an American naval ship operating in the Far East. The targets made nine passes near the ship at a calculated speed of approximately 3,000 miles per hour. Although the radar operator tracked these targets clearly on his scope, no visual sightings were reported, and only one pass appeared to originate directly over the Guadalupe itself.

The radar equipment functioned normally during the observations. The radar blips (the bright spots that represent detected objects) appeared elongated to about 3/8 of an inch when the target made runs on Guadalupe from 15 miles away, and to 1/8 inch on retiring runs made near the patrol plane. The targets were tracked out to a distance of 30 miles. The radar operator believed the target came from directly overhead and only appeared on the scope when it entered the radar's detection range. Conditions were partly cloudy, with cloud cover between 5 and 6/10 at 3,000 feet.

Analysts at Air Force headquarters requested extensive additional information before they could evaluate the sighting. They asked for details about the radar equipment itself, its frequency, and whether the target signals were steady or spotty. They also wanted to know the aircraft's altitude, whether the targets appeared on other radars, and what other aircraft were in the area. In their preliminary assessment, the Air Force suggested the targets could have been caused by interference from another radar set, interference from the detecting radar itself, weather effects, or possibly an unknown airborne target.

A separate report filed in March 1951 noted that similar high-speed radar targets had been detected in the same region before, and analysts suggested that abnormal weather conditions might have caused the radar signals, with weather targets sometimes appearing to move at very high speeds while actually remaining stationary. The full case file, 15 pages as held by the National Archives, is reproduced below.