JAL 123

Japan Airlines Flight 123
日本航空123便

JA8119, the aircraft involved the accident, photographed at Osaka International Airport in 1984
Accident summary
Date	August 12, 1985
Summary	In-flight structural failure resulting from incorrect repairs to tailstrike damage
Site	Mount Osutaka-no-one Ueno, Gunma Prefecture, Japan 36°0′5″N 138°41′38″E / 36.00139°N 138.69389°E / 36.00139; 138.69389Coordinates: 36°0′5″N 138°41′38″E / 36.00139°N 138.69389°E / 36.00139; 138.69389
Passengers	509
Crew	15
Fatalities	520
Injuries (non-fatal)	4
Survivors	4
Aircraft type	Boeing 747SR-46
Operator	Japan Airlines
Registration	JA8119
Flight origin	Haneda Airport, Tokyo
Destination	Osaka Int'l Airport, Itami

Japan Airlines Flight 123 (日本航空123便, Nihonkōkū 123 Bin) was a scheduled domestic Japan Airlines passenger flight from Tokyo's Haneda Airport to Osaka International Airport, Japan. On Monday, August 12, 1985, a Boeing 747SR operating this route suffered an explosive decompression 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 (御巣鷹の尾根, Osutaka-no-One), near Mount Osutaka.

The explosive decompression was caused by a faulty repair performed by Boeing after a tailstrike incident during a landing seven years earlier. A doubler plate on the rear bulkhead of the plane was improperly repaired, compromising the plane's airworthiness. Cabin pressurization continued to expand and contract the improperly repaired bulkhead until the day of the accident, when the faulty repair finally failed, causing the explosive decompression that ripped off a large portion of the tail and caused the loss of hydraulic controls to the entire plane.

Casualties of the crash included all 15 crew members and 505 of the 509 passengers; some passengers survived the initial crash but subsequently died of their injuries hours later, mostly due to delays in the rescue operation. It is the deadliest single-aircraft accident in history, the deadliest aviation accident in Japan, the second-deadliest Boeing 747 accident and the second-deadliest aviation accident after the 1977 Tenerife airport disaster.

The accident aircraft was registered JA8119 and was a Boeing 747-146SR (Short Range). Its first flight was on January 28, 1974. It had more than 25,000 airframe hours and more than 18,800 cycles (one cycle equals one takeoff and landing).