How the plane in China went from cruising altitude to disaster
Crashes during the cruise phase of flights are relatively rare, even though this period accounts for the majority of flight time. Crashes during the descent stage, when the plane first leaves cruising altitude, are even more uncommon
Flight MU5735 was en route from Kunming, the capital of the southwestern province of Yunnan, to the port city of Guangzhou on March 21 when it suddenly plunged from cruising altitude and crashed in the mountains of Guangxi, killing all 132 people onboard.
Investigators are hoping the flight recorders, or "black boxes", can give clues as to what could have caused the plane to plummet at such a steep angle and slam into the mountains at high speed.
Abrupt descent
FlightRadar24 collected Automatic Dependent Surveillance-Broadcast (ADS-B) data, which was streamed directly from the aircraft's computers during its flight. Reuters plotted this data to illustrate the plane's movements and how it suddenly descended.
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The plane had been cruising at 29,100 feet at 2:20 p.m. local time and was traveling along a similar path to flights from previous days.
Suddenly, the aircraft dived to 7,425 feet before recovering briefly and climbing to 8,600 feet, then descended rapidly again, FlightRadar24 data showed. The last tracked altitude was 3,225 feet above sea level.
Reuters compared the trajectory of the dive to other major commercial airline crashes in recent years as well as select historic crashes for which suitable data was available. Some have very different descents as they crash during different phases of flight – for example, during landing.
Two crashes appear to descend at a similar rate: Sriwijaya Air flight 182, which crashed during takeoff from Jakarta in January 2021, and SilkAir flight 185, which crashed in a steep dive near the Indonesian city of Palembang. The cause of the SilkAir crash is disputed.
Two other crashes involved falls from even greater altitude before impact: Air France 447, which crashed into the Atlantic Ocean in 2009 after stalling, and AirAsia 8501, which crashed into the Java Sea in 2014, less than halfway into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore.
Comparing crash profiles
The data showed the aircraft plunged at a rate of 31,000 feet per minute – the height of a 50-storey building every second – through certain stages of the descent. The plane recorded this same vertical speed of descent on its last reading before losing contact, indicating the plane was most likely still diving at an extreme rate before impact.
Transitioning to descent stage
The crashed aircraft dived around the time it would usually leave the cruise phase of flight and begin its descent.
Crashes during the cruise phase of flights are relatively rare, even though this period accounts for the majority of flight time. Crashes during the descent stage, when the plane first leaves cruising altitude, are even more uncommon.
The same flight number a day earlier began a normal, gradual descent from the same altitude, also at 2:20 p.m., and landed safely in Guangzhou, according to FlightRadar24. Data show that several flights over the previous week had followed similar paths before making an approach to the airport from the north or south.
Data show the abruptness of the crashed aircraft's change in course and its extreme rate of descent.
An aviation official said the 737-800 jet that crashed had met airworthiness standards before take-off and crew members had been in good health.
The plane had three pilots on board on its final flight, Zhu Tao, an official from the aviation authority, said at a news conference, which is one more than normally required on a 737.
The aircraft did not respond to repeated calls from air controllers during its rapid descent, Zhu said. This is not necessarily unusual, experts say, as radio communications are low priority during a serious flight emergency.
Crash site
Emergency workers on the ground have been scouring the forest-covered mountains of China's southern Guangxi region for victims and clues as to what happened. No survivors have been found so far.
The crash site is hemmed in by mountains on three sides with access provided by just one path. Rescuers have recovered both of the two black boxes, which have been sent to Beijing. It is too early to determine the cause of the crash; experts say such accidents are usually the result of a combination of factors.
