NORTH Korea, October 1952October 1952

On the morning of October 16, 1952, two U.S. Air Force pilots flying a T-6 training aircraft over North Korea spotted an unidentified object near the main line of resistance. First Lieutenant Thomas A. O'Neill, piloting from the back seat, noticed what he thought was an unusual aircraft flying at 6,000 feet on an easterly heading at roughly 200 mph. He alerted First Lieutenant William H. Hooper, the instructor pilot, who was flying the T-6 at 6,300 feet.

Both pilots described the object as perfectly circular, about 25 feet in diameter, with a metallic silver color and a slight glow. It had no visible wings, tail, propeller, or other aerodynamic features. As the T-6 maneuvered closer, the object appeared to slow down and then stopped, hovering silently over a grid position near the coast. The pilots differed slightly on how long it hovered, with Hooper estimating around 15 seconds and O'Neill reporting 1 to 2 seconds. When Hooper dipped the aircraft's right wing for a better look, the object suddenly accelerated in an east-northeast direction at an estimated 800 mph, disappearing into the haze over the ocean. The entire sighting lasted about three minutes, from 6:50 a.m. to 6:53 a.m. Neither pilot observed any sound, vapor trail, or visible means of propulsion.

Air Force intelligence officers interviewed both pilots and found them credible. Both were in their thirties, level-headed, and had flown combat missions before. They had made all their estimates by comparing the object to known aircraft like the F-51 Mustang. They initially ruled out a weather balloon because the object appeared to be solid metal and perfectly circular rather than flexible.

However, the investigation uncovered a possible explanation. Intelligence records showed that enemy forces had been operating a large captive balloon (a balloon held in place by a cable) in the same general area since at least June 1952. The balloon's known position, about 4,500 meters away from where the pilots saw their object, lined up almost directly with the sighting location. Military intelligence suggested the pilots may have observed this captive balloon after it was released or had broken loose. Wind conditions that morning, blowing from the southwest at 20 to 25 knots per hour, could have carried the balloon in a southeast direction. If the pilots saw it rising uncontrollably, the motion caused by the wind and changes in air currents might have made a stationary or slowly rising balloon appear to accelerate away. An air pocket or sudden wind shift could explain why the object seemed to hover briefly.

The Air Force's official conclusion, marked "Probably Balloon," leaned toward this explanation, though the file notes that the pilots themselves had dismissed the weather balloon possibility during their interviews because of how solid and perfectly round the object looked.

The full case file, comprising 10 pages as held by the National Archives, is reproduced below.