Fuel switches of a China Eastern flight that crashed into a hillside in 2022 were likely deliberately cut off, according to a report by a US government federal agency charged with investigating civil aviation accidents.

All 132 people on board died after the Boeing 737 aircraft crashed into a mountain in the remote Guangxi region on 21 March 2022. The China Eastern Airlines flight MU5735 was en route from the southwestern city of Kunming to Guangzhou.

While the Chinese government is yet to release a final report on the incident, the findings released by the US National Transportation Safety Board (NTSB) support the speculation that the pilots had intentionally caused China's deadliest air disaster in decades.

The NTSB revealed that the switches controlling the flow of fuel to both engines were moved to the "cut-off" position while it was at a cruising at an altitude of 8,839m.

“The fuel switches on both engines moved from the run position to the cut-off position," the aviation body said. It added: "Engine speeds decreased after the fuel switch movement."

There was no sign that the fuel switches were ever flipped back on to attempt to bring the engine back to life.

The US aviation body is supporting the Chinese authorities because Boeing is an American plane manufacturer. The report was released earlier this month under the Freedom of Information Act.

The impact was so severe that the aircraft broke apart into around 40,000 pieces, according to reports. The damaged cockpit voice and flight data recorders survived the crash and were recovered for investigation.

The aviation safety office director at the Chinese aviation authority said they did not have a clear assessment of the cause for the crash. He claimed that air controllers had repeatedly called the aircraft during its descent but had received no response.

The Civil Aviation Administration of China had argued that the crew held valid licences, were adequately rested, and passed health checks.

Neil Campbell, a former air safety investigator at the Australian Transport Safety Bureau, said it was routine for jet fuel switches to be turned off after the plane has landed, but almost never in flight. He told Bloomberg News that the actions looked like a “deliberate event".

“There’s no reason for switching the engines off, so that’s the bit that’s highly unusual,” Mr Campbell said.

Tony Stanton, an aviation expert at Strategic Air, told CNN that the new data “does not by itself prove motive, intent or who moved the switches”.

What the data show is “very difficult to reconcile with a conventional dual-engine mechanical failure and is much more consistent with [human] commanded fuel shutoff”, Mr Stanton said.

The fuel switch movement has also been at the centre of the ongoing investigation into 2025 Air India flight crash that killed all but one person on board.

The London-bound Boeing 787-8 Dreamliner with 242 people on board crashed moments after taking off on 12 June, erupting in a fireball after hitting a medical college hostel.Another 19 people were killed on the ground when the plane crashed onto a medical college hostel during lunch hour.

The final report into the investigation is yet to be released.