According to the released data, the fuel control switches for both engines on the China Eastern Airlines Boeing 737-800 moved from RUN to CUTOFF approximately 23 seconds before the FDR stopped recording. The autopilot disengaged at the same point. Roughly three seconds later, one of the cockpit yokes was pushed forward, sending the aircraft into the near-vertical descent that has defined the publicly known footage of the loss.

What the China Eastern MU5735 data shows

The NTSB release, as reported by CNN, is a partial dataset rather than a finding of cause. It does not establish which pilot manipulated the fuel switches or the yoke, nor does it rule out a system fault that could have driven the cockpit indications. China’s Civil Aviation Administration leads the official MU5735 investigation; CAAC has not publicly responded to the FOIA release as of publication.

AirLive and Simple Flying both report the FDR contents are consistent with publicly available trajectory data — a steep, sustained nose-down attitude that did not recover. The aircraft was at FL290 when control was lost on a routine domestic sector from Kunming to Guangzhou.

The Boeing 737-800 fuel control switches sit on the centre pedestal between the two pilots and require a deliberate movement past a detent to leave the RUN position. Industry sources describe inadvertent activation as unlikely but not impossible. The same family of switches is at the centre of the still-open investigation into the 2024 Air India 171 fuel-cutoff event, and the NTSB has now publicly tied data on two separate fatal events to the same cockpit input.

China Eastern MU5735 investigation timeline

China’s investigation into MU5735 is now in its fifth year. The CAAC has issued two preliminary statements since the crash but has not published a final report. Chinese officials previously declined to share complete FDR contents internationally, which is why a third-party FDR analysis emerged through the NTSB FOIA process rather than through CAAC’s own investigation channels.

The aircraft, registered B-1791 and ten years old at the time of the loss, had no recorded airworthiness issues prior to the flight. Maintenance records, crew duty records and any cockpit voice recorder content remain under CAAC seal. Independent analysts have been working from limited Chinese disclosures since 2022, and the NTSB material is the first authoritative timeline of the cockpit inputs in the final seconds of recording.

Why a US agency held Chinese flight data at all

The route by which this material became public is worth understanding, because it is unusual and it explains the friction.

Under ICAO Annex 13, the state where an accident occurs leads the investigation — here, China. But the states of design and manufacture are entitled to appoint accredited representatives, and the Boeing 737 and its engines are US products. That entitlement is how the NTSB came to hold data from a crash in Guangxi in the first place: not as an investigator in its own right, but as a participant supporting the CAAC’s inquiry.

Records held by a US federal agency are subject to the Freedom of Information Act regardless of where they originated. So a FOIA request filed in January 2026 reached material that China’s own investigation had not published — which is why the first authoritative public account of the final seconds came out of Washington rather than Beijing, four years after the loss.

What the release changes

The NTSB FOIA release does not close the China Eastern MU5735 investigation, but it does shift the public discussion. AeroTime characterises the pattern of inputs as suggestive of a deliberate act in the cockpit; the NTSB material itself stops short of that conclusion.

For aviation safety investigators, the release also has procedural implications. It is unusual for FDR contents from a non-US accident to surface via a US FOIA request before the host-state investigator has published. CAAC’s response — whether it now releases its own technical analysis, contests the NTSB material, or maintains silence — will set a template for how future Chinese-host accident investigations interact with international counterparts.

The Air India 171 inquiry remains separately open, and the cockpit-action pattern in that case is being analysed independently. Pilot-input questions on the 737 family are likely to be a continuing thread for both investigators and operators through 2026.

AircrewNews will update this article when CAAC issues a public response or releases its own analysis of the China Eastern MU5735 flight data.

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Squawk 7700 over the Atlantic

Flight AC853, a 777-300ER registered C-FITL, departed Heathrow at 08:34 BST. The aircraft climbed to its initial cruising altitude of FL340 and was tracking west over the Atlantic when the crew transmitted a squawk 7700 emergency code at 09:30 BST, according to AirLive.

What squawk 7700 actually means

A transponder replies to radar with a four-digit code, and three of those codes are reserved worldwide. 7500 indicates unlawful interference, 7600 a radio communications failure, and 7700 a general emergency. Setting 7700 flags the aircraft on every controller’s display in range and buys the crew immediate priority — direct routing, protected airspace and emergency services on arrival.

The key point for reading a story like this one is that 7700 carries no information about severity or cause. It covers a technical malfunction, a medical event in the cabin, a pressurisation problem or a precautionary call by a crew who would rather have the airspace cleared than negotiate for it. A 7700 that ends in an uneventful landing with no injuries is a normal outcome, not a near-miss.

Why turn back rather than press on

Turning around mid-ocean rather than continuing to a North American alternate is standard practice for an unresolved fault. Once past the point where a return is straightforward, a North Atlantic crossing commits an aircraft to hours over water with a limited set of diversion fields — Keflavík, Shannon, Gander — none of which offers what a major hub does.

Heathrow, roughly an hour behind them, offered full emergency response for the Air Canada crew, the operator’s own engineering support and hotel and rebooking capacity for a full widebody load. Crews weigh landing weight in that decision too: an aircraft that has just tankered fuel for a transatlantic sector is well above its maximum landing weight, so a return usually means either holding to burn fuel down or accepting an overweight landing and the inspection that follows. Neither is an emergency in itself; both take time, which is part of why the aircraft was airborne for around 90 minutes on a flight that never left the region.

The Air Canada Heathrow return

The Air Canada Heathrow return ended on runway 27L at approximately 10:02 BST. Emergency vehicles met it at the gate. None of the occupants were injured.

Travel And Tour World reported that the cause of the emergency had not been disclosed by Air Canada at the time of publication. Yorkshire Live noted the aircraft was met at the gate by ground emergency response — standard procedure for any arrival squawking 7700, regardless of cause.

Who would investigate an Air Canada Heathrow diversion

Not every Air Canada Heathrow emergency becomes a formal investigation. The UK Air Accidents Investigation Branch has jurisdiction over occurrences in UK airspace, and Transport Canada has an interest as the regulator of the operator and the state of registry, but a reportable occurrence has to clear a threshold — serious injury, significant damage, or a safety issue with wider implications. A precautionary return that lands normally with no injuries frequently does not, and is handled through the operator’s own safety management system and routine occurrence reporting instead.

That is the most likely reason no findings have been published, and why none may be. Absence of an investigation report here is not evidence that something is being withheld.

The route and the type

The 777-300ER is the workhorse widebody for Air Canada’s transatlantic operations, and Heathrow–Toronto is one of the carrier’s highest-frequency routes on that side of the Atlantic, typically flown multiple times a day. That density matters operationally on Air Canada Heathrow services: a carrier with several daily rotations on a route can absorb one aircraft going technical far more easily than one flying it three times a week, which is why the disruption from an event like this is usually measured in hours rather than days.

AircrewNews will update this story if Air Canada or the UK Air Accidents Investigation Branch publish further information.

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