On August 12, 1985, a Japan Airlines B-747 aircraft lost, shortly after take-off, part of its tail and crashed in the mountains northwest of Tokyo. Of the 524 persons on board 520 were killed, 4 survived the accident. The accident was caused by a rupture of the aft pressure bulkhead of the aircraft, and the subsequent ruptures of a part of the fuselage tail, vertical fin and hydraulic flight control systems. The rupture happened as the result of an improper repair after an accident with the aircraft in Osaka, in June 1978.