Project Blue Book Case #886. On February 1, 1951, an unidentified object was observed at Johnson Air Base (now Iruma Air Base) near Tokyo — the headquarters of the Fifth Air Force, which commanded all USAF combat operations during the Korean War. Johnson AB was the nerve center from which air campaigns over Korea were planned and directed.
The Fifth Air Force's commander at Johnson controlled the fighter, bomber, and reconnaissance units that engaged Communist forces daily over the Korean Peninsula. The base's intelligence staff processed combat reports and reconnaissance data from across the theater. An unidentified object over this command center was a matter of the highest operational concern.
February 1951 was during the Korean War's most desperate phase — Chinese forces had entered the conflict and pushed UN forces south of Seoul. The case was classified "Unknown."