The Crash Of Japan Airlines Flight 123 And Its Subsequent Effects On Aviation

A photo of the airplane that was involved in the accident, JA8119, from 1984.

Although airplanes are currently known as one of the most reliable and safe ways to travel long distances, aviation accidents continue to happen today. However, the number of such accidents today dwarfs in comparison to those just a few decades ago. Aviation accidents are less common today primarily because of the lessons we learned from past accidents and the changes we subsequently implemented across the aviation industry. One of these earlier accidents is the crash of Japan Airlines (JAL) Flight 123 on August 12, 1985. This accident is infamous for being the deadliest accident involving one aircraft. Despite being a very unfortunate disaster, the crash served as a stepping stone for the implementation of better safety standards.

The Flight and Its Route

JAL Flight 123 was a regularly scheduled domestic flight from Tokyo’s Haneda Airport to Osaka International Airport. It was operated using a Boeing 747-SR100, which is a variant of the 747 aircraft designed specifically for shorter flights.

On the summer evening of the tragedy, the plane was carrying 509 passengers and 15 crew members. Most passengers consisted of business travelers or families returning home. The flight also included well-known figures such as the popular Japanese singer Kyu Sakamoto. The plane rolled down the runway and lifted off at 6:12 P.M. for what should have been a brief one hour flight.

The Catastrophic Failure

Twelve minutes after takeoff, at about 24,000 feet, the plane suffered a massive structural failure. The rear pressure bulkhead—a crucial component of all aircraft that has the function of sealing the cabin and maintaining air pressure—suddenly gave way.

The force of the resulting explosive decompression tore off a large section of the plane’s tail, severed all four hydraulic lines, and made the flight controls unresponsive. Hydraulic systems control everything from rudders and elevators to ailerons, and with them gone, the aircraft became nearly impossible to steer or control.

The Crew’s Struggle

Captain Masami Takahama, First Officer Yutaka Sasaki, and Flight Engineer Hiroshi Fukuda faced a nightmare scenario. Without hydraulics, conventional control of the aircraft was impossible.

For the next 32 minutes, the crew tried to maneuver the aircraft using only engine thrust. They noticed that by increasing power to engines on one side of the aircraft and reducing power to those on the other side, they could turn the aircraft. However, while it gave the flight crew a glimmer of hope, this method was not too effective, and the plane continued to drift north over mountainous terrain, far from its intended route to Osaka.

Cockpit voice recordings (CVRs) later showed the crew’s professionalism as they fought against horrible odds. They communicated with Tokyo air traffic control, declaring an emergency and requesting an immediate return to Haneda. Controllers attempted to guide and help them, but with no meaningful flight controls at their hand, the flight crew could only hope to keep the aircraft stable long enough for an emergency landing.

The Crash on Mount Takamagahara

The planned and actual flight paths of JAL Flight 123 on the evening of August 12, 1985.

At 6:56 P.M., about 44 minutes after takeoff, JAL Flight 123 hit Mount Takamagahara, which is located roughly 62 miles (100 kilometers) from Tokyo. The crash tore the aircraft apart, and fire consumed much of the wreckage.

Miraculously, of the 524 people that were on board, four survived: three women and one child. They were all seated toward the rear of the plane. Their survival was attributed to their location, which shielded them from the worst of the impact. The deaths of 520 people made this the deadliest single-aircraft accident in history, a record that still stands today. 

Rescue Efforts and Delays

The crash site was located in a remote mountainous area, making rescue operations extremely difficult. In addition, the crash was so violent that emergency response crews assumed that there would be no survivors. As a result, they did not move as quickly and took 14 hours to reach the crash site. However, when the rescuers finally reached the crash site, they found that four people had actually survived.

The delay in rescue efforts sparked criticism. It is believed that if the rescue teams had been more proactive, countless others could have been saved. This controversy highlighted the importance of improving emergency response systems as well, not just preventing accidents.

The Investigation

The Japanese government, assisted by Boeing and the U.S. National Transportation Safety Board (NTSB), launched an in-depth investigation on the airplane’s past and what could have caused the accident. 

During this investigation, they concluded that it was due to improper repairs that had taken place in 1978. Seven years before the crash, the same aircraft had experienced a tailstrike incident during landing, damaging its rear pressure bulkhead. Boeing has carried out repairs, but investigators found that the bulkhead had not been fixed properly. Instead of using a continuous doubler plate, which would have restored its strength, mechanics had incorrectly used two separate pieces, leaving the joint vulnerable.

Over thousands of pressurization cycles, as the plane ascended and descended, tiny cracks formed along the faulty repair. Eventually, these cracks spread until the bulkhead could no longer withstand the stress put upon it by pressurization at cruising altitude. Seven years later, the seemingly small mistake made by the Boeing technicians led to its catastrophic rupture.

When the bulkhead failed and caused an explosive decompression, the resulting debris severed all four hydraulic lines. This left the pilots with no conventional control over the aircraft, leaving them in a hopeless situation. In the final report, the crash was attributed to the maintenance error in 1978. Simply put, the failure to properly repair the bulkhead ultimately doomed the flight.

Impact on Aviation

A digital composite (not an actual photograph) of JAL Flight 123 flying with a missing tail section.

The Flight 123 disaster had far-reaching consequences for aviation safety, maintenance standards, and airline culture. Airlines worldwide heavily tightened maintenance checks, with focus on older aircraft and previously repaired structures. Bulkhead inspections became more rigorous, and regulators introduced much stricter requirements for documenting and reviewing repairs so such an accident didn’t happen again.

The crash of JAL Flight 123 highlighted the vulnerability of aircraft to complete hydraulic failure. While jets at the time were already equipped with multiple redundant systems, engineers looked for new technologies to increase the chances of survival if an incident similar to JAL 123 were to happen again. Later aircraft like the Airbus A320 included computerized flight control backups, helping reduce the chances of hydraulic failure.

CRM training, which was already being developed after the Tenerife disaster in 1977, also became a universal requirement. While the Flight 123 crew performed incredibly well even under pressure, the crash still reinforced global emphasis on teamwork and communication in cockpits. 

The Human Side

Among the most poignant details of the disaster were the farewell notes written by passengers in the final 30 minutes of the flight. With the plane uncontrollable but still airborne, many had time to write last messages to loved ones. These notes were later recovered, and they reflected bravery, love, and sorrow in the face of certain death.

Such personal stories underscored the human cost of aviation accidents and strengthened public demand for reforms surrounding safety in aviation.

Legacy of Flight 123

Nearly four decades after the crash, the crash of JAL Flight 123 still remains a crucial part of aviation history. It demonstrated how a single maintenance error could come back to bite years later.

The legacy of JAL Flight 123 is also one of resilience and progress. The reforms inspired by the disaster improved maintenance procedures, safety oversight, and technological innovation. The lessons continue to shape aviation and help protect lives today.