Photo of Japan Air Liner
Photo of Japan Air Liner
Photo copyright Michel Gilliand - used with permission
Accident Perspectives:
Airplane Life Cycle
  • Maintenance / Repair / Alteration
Accident Threat CategoriesGroupings
  • Structural Failure
  • Lack of System Isolation / Segregation
  • Pressurization / Decompression Failures
  • Loss of Control
Accident Common Themes
  • Organizational Lapses
  • Human Error
  • Flawed Assumptions

Japan Airlines Flight 123, Boeing 747-SR100, JA8119

Location: Gunma Prefecture, Japan

Date: August 12, 1985


Approximately 12 minutes after departing Tokyo bound for Osaka, and just prior to reaching its planned cruising altitude of 24,000 feet, JAL 123 experienced an explosive decompression, caused by a rupture of the airplane's aft pressure bulkhead. The resultant pressure surge into the unpressurized area aft of the pressure bulkhead resulted in extensive damage to the airplane. The airplane's Auxiliary Power Unit (APU), rudder, and a large portion of the vertical stabilizer were lost. Additionally, all four of the airplane's hydraulic lines were severed, resulting in complete hydraulic pressure loss which severely degrading the airplane's controllability. Despite severe pitch (phugoid) and lateral-directional (dutch-roll) oscillations the airplane managed to stay airborne for approximately 30 minutes after the event before crashing in remote mountainous terrain in Gunma Prefecture. Out of the 524 passengers and crew aboard only four survived.

The root cause of the explosive decompression was attributed to an improperly executed repair to the airplane's aft pressure bulkhead that was completed several years prior to the accident. The improper repair led to undetected local fatigue cracking which undermined the bulkhead's strength, and resulted in a catastrophic failure of the entire bulkhead.