Today, the Civil Aviation Administration of China (CAAC) released the preliminary report on its investigation of the crash of China Eastern Airlines Flight MU5735. On March 21, 2022, the flight crashed under extremely mysterious circumstances during a flight from Kunming to Guangzhou.

In accordance with the Chicago Convention on International Civil Aviation, the country in charge of an airline accident investigation should submit a preliminary investigation report to the International Civil Aviation Organization within 30 days of the accident. The CAAC’s report meets that requirement; at this time, however, the report is unable to shed much light on the cause of the accident because the crash almost totally destroyed the airframe and engines and badly damaged the flight data recorder (FDR) and cockpit voice recorder(CVR). Efforts to retrieve and analyze crucial data from those devices continue.

This is Flightradar24’s depiction of the final minutes of MU5735 based on ADS-B flight tracking data collected from the plane in real time.


After a normal flight, MU5735 abruptly and rapidly descended from an altitude of 29,000 ft. (8,839m) and crashed within a span of about two minutes.

The CAAC’s preliminary report states that the aircraft received all required maintenance checks in a timely manner, the flight crew and cabin crew met all qualification requirements, the cargo contained no goods that were declared to be dangerous, no dangerous weather was forecast, radio communication with the flight was normal prior to the incident, and when the aircraft suddenly dropped from its cruise altitude, an air traffic controller called the crew immediately, but never received any reply.

The report also states that the trailing edge of the right wingtip winglet was found approximately 12 kilometers (7.5 miles) from the main impact point. Winglets are used on many types of airliners. They are the part of the wingtip that is perpendicular to the rest of the wing. Winglets are used to improve fuel efficiency by minimizing drag from vortices that trail from the wingtip during flight.

My Interpretation

It is incredibly rare for a commercial passenger airliners to drop from cruising altitude and crash. The CAAC preliminary report mentions one new and potentially significant fact but fails to explain another previously known anomaly.

In a prior post, I discussed causes of other airline accidents such as an aerodynamic stall, mechanical problems, and even intentional acts that might be responsible for the crash of MU5735. I also noted that the co-pilot had logged over 31,000 hours of flight time. The captain had almost 7,000 hours of flight time. I think it is unusual for an airline pilot to have so much flight time and not be working as a captain. The CAAC preliminary report does not address the reason for this unusual situation unfortunately.

A security camera caught the plane’s final dive on video. From the low-quality video, the plane appeared intact. Finding a piece of winglet 12km from the impact indicates that this piece separated from the plane at some altitude. Given the fairly remote location, it is possible that other small pieces came of the aircraft before or during the high-speed dive and have not been found.

Final Thoughts

So far, the curious case of China Eastern Flight MU5735 is an enigma. Given the almost total destruction of the airframe and engines, the cause of this very puzzling and extremely rare incident will likely remain unresolved until the data from the FDR and CVR are retrieved and analyzed. Presently, it is unknown when or even if that will happen. I’ll keep an eye out for further developments.