Japan Airlines Flight 123 was a scheduled domestic Japan Airlines passenger flight from Haneda Airport (Tokyo International Airport) to Osaka International Airport, Japan. On Monday, August 12, 1985, a Boeing 747SR operating this route suffered mechanical failures 12 minutes into the flight and, 32 minutes later, crashed into two ridges of Mount Takamagahara in Ueno, Gunma Prefecture, 100 kilometres (62 miles) from Tokyo. The crash site was on Osutaka Ridge (Osutaka-no One), near Mount Osutaka. All 15 crew members and 505 of the 509 passengers on board died, resulting in a total of 520 deaths and 4 survivors.
It is the deadliest single-aircraft accident in history, and the second-deadliest accidental plane crash, behind the Tenerife airport disaster. The fatalities added to August 1985 being commercial aviation's single deadliest month for passengers plus crew, part of the single deadliest such year.
The survivors were:
Ochiai Yumi, an off-duty JAL flight attendant, age 25, who was jammed between seats;
Yoshizaki Hiroko, a 34-year-old woman and her 8-year-old daughter Mikiko(Yoshizaki Mikiko), who were trapped in an intact section of the fuselage;
Kawakami Keiko, a 12-year-old girl, who was found wedged between branches in a tree. Kawakami's parents and younger sister died in the crash, and she was the last survivor to be released from hospital. She was treated at the Matsue Red Cross Hospital in Matsue, Shimane Prefecture before her release on Friday, November 22, 1985.
Among the dead were singer Sakamoto Kyu and Japanese banker Yukawa Akihisa, the father of solo violinist Diana Yukawa.
The official cause of the crash according to the report published by Japan's Aircraft Accident Investigation Commission is as follows:
1.The aircraft was involved in a tailstrike incident at Osaka International Airport seven years earlier as JAL115, which damaged the aircraft's rear pressure bulkhead.
2.The subsequent repair of the bulkhead did not conform to Boeing's approved repair methods. The Boeing technicians fixing the aircraft used two separate doubler plates, one with two rows of rivets and one with only one row when the procedure called for one continuous doubler plate with three rows of rivets to reinforce the damaged bulkhead. The incorrect repair reduced the part's resistance to metal fatigue by 70%. According to the Federal Aviation Administration, the one "doubler plate" which was specified for the job (the Federal Aviation Administration calls it a "splice plate" - essentially a patch) was cut into two pieces parallel to the stress crack it was intended to reinforce, "to make it fit". This negated the effectiveness of two of the rows of rivets. During the investigation, Boeing calculated that this incorrect installation would fail after approximately 10,000 pressurizations; the aircraft accomplished 12,318 successful flights from the time that the faulty repair was made to when the crash happened.
3.When the bulkhead gave way, the resulting explosive decompression ruptured the lines of all four hydraulic systems and blew off the vertical stabilizer. With the aircraft's flight controls disabled, the aircraft became uncontrollable.