Sea of Japan E of Vladivostok, December 1957December 1957

On December 23, 1957, the commander of a U.S. Air Force reconnaissance aircraft spotted a projectile streaking across the sky over the Sea of Japan east of Vladivostok. The object had a long trail behind it and traveled in an arcing path before disappearing in what the pilot described as a very bright explosion, like a flash bomb. The sighting lasted only seconds, at an unknown distance from the aircraft.

What made this sighting unusual was what happened to the aircraft's radar. The radar system was jammed starting at 0243 (12:43 a.m.) and continued until 0244 Zulu time. The jamming signal was continuous, and the radar operators could not retune the equipment to filter it out. No radar targets were visible during the jamming period. The aircraft was flying at 35,000 feet on a true heading of 247 degrees.

An Air Force intelligence officer reviewing the case noted that there was insufficient radar data to determine what had occurred. The officer also mentioned that the Far East region had recently seen a large number of unusual electronic signals and definite evidence of jamming activity. However, the case file does not state a final conclusion about what the object was. The full case file, including supporting documents and communications between military commands, is reproduced below as held by the National Archives in 8 pages.