The fuel supply to both engines of a China Eastern Airlines flight was cut off before the jet plunged into a hillside in southern China in March 2022, killing all 132 people on board, according to data released by US aviation investigators — a finding that closely parallels what Indian investigators reported in a preliminary analysis of the Air India flight 171 crash in Ahmedabad last year. The jets were different models, but both manufactured by Boeing.
The US National Transportation Safety Board (NTSB) released the data this week in response to a freedom of information request, Reuters reported. Originating from the Boeing 737-800’s flight data recorder (FDR), it found that “while cruising at 29,000 ft, the fuel switches on both engines moved from the run position to the cutoff position. Engine speeds decreased after the fuel switch movement.”
The final moments of the flight were recorded by a security camera of a local mining company and showed the plane in a near-vertical dive seconds before it struck the ground — a flight profile that experts at the time believed was unusual.
While the fuel control switches on Boeing 737 and the Boeing 787 – the type that was flight 171 – are different, their mechanisms are identical: A pilot must pull each switch up before moving it from the run to the cutoff position, a deliberate design to prevent inadvertent activation.
The FDR data captured the switch movement but ended before the aircraft hit the ground — cutting out at approximately 26,000 feet, still in descent, the NTSB disclosure stated. The recorder has no battery backup; once engine speeds fell and the aircraft’s generators went offline, it powered down.
The cockpit voice recorder is a different matter. It “does have a battery backup and can continue recording for at least 10 minutes after the loss of the aircraft generators,” the NTSB report noted — meaning it likely captured crew conversation through much of the subsequent descent. Chinese authorities have not publicly released its contents.
India’s Aircraft Accident Investigation Bureau (AAIB) established in its preliminary report on Air India Flight 171, which crashed shortly after takeoff from Ahmedabad on June 12, killing 260 people, including 229 onboard. The AAIB found that the fuel control switches on the Boeing 787’s two engines transitioned from run to cutoff three seconds after the aircraft became airborne, one second apart, before pilots attempted to restore fuel flow. Both engines began relight sequences but the aircraft had insufficient altitude to recover.
In the China Eastern case, the civil aviation administration of China (CAAC), which formally led the investigation, has not released a final report and has given no public update for more than two years. China Eastern Airlines and the CAAC did not respond to questions, and a spokesman for China’s ministry of foreign affairs declined to comment at a regular briefing on Wednesday, Reuters added.
The NTSB’s role in the MU5735 investigation was as the US accredited representative under international aviation protocols, given that the 737-800 is manufactured by Boeing, an American company. The flight data recorder was sent to the NTSB laboratory in Washington for analysis.
The crash of MU5735 remains China’s deadliest air disaster in decades.
