Kaisong, Korea, November 1957November 1957

On November 5, 1957, at approximately 2030 (8:30 p.m.) GMT, nineteen men of the 1st Army Corps stationed in the demilitarized zone of Korea observed a bright flash of light in the western sky. The flash was described by witnesses as blue-white in color, developing into a reddish-orange trail of flame. The object appeared roughly 1 to 1.5 inches in size when held at arm's length. The bright flash lasted between 2 and 4 seconds. A trail of smoke, resembling a jet vapor trail, remained visible for 5 to 30 minutes depending on the observer.

Most witnesses reported the object moving at approximately 15 degrees elevation, though some indicated angles between 60 and 70 degrees. The azimuth (compass direction) was consistently reported as 270 degrees, roughly due west. Most observers stated the object traveled in a horizontal flight path, though a few noted a slight zigzag pattern. The phenomenon was so bright that wildlife in the area, including pheasants, became alarmed.

The U.S. Air Force investigators ruled out several conventional explanations. The sighting's characteristics made it unlikely to be a meteor, fireball, or the Soviet satellite then in orbit. The length and luminosity of the vapor trail, combined with reports from multiple credible military observers, suggested a high-altitude, high-velocity object. Investigators considered whether the object might represent a Soviet missile or an advanced type of rocket undergoing re-entry, which could provide data on re-entry dynamics problems.

However, the file notes that the inconsistency in observer estimates (sighting duration ranged from 2 seconds to nearly 20 minutes) and the inability to conduct on-site investigations made definitive analysis difficult. The Air Force evaluation ultimately concluded the object was unknown, pending receipt of further information or data from intelligence sources. The full case file is reproduced below as held by the National Archives across 41 pages of microfilm T1206, Roll 30.