GUANGZHOU, China (Reuters) A China Eastern Airlines (NYSE:CEA) Boeing (NYSE:BA) 737-800 with 132 people on board crashed in mountains in southern China on Monday after a sudden plunge from cruising altitude at about the time when it would normally start to descend ahead of its landing.
Media said there were no signs of survivors on the domestic flight.
The airline said it deeply mourned the passengers and crew, without specifying how many people had been killed on the jet, an earlier model to the 737 MAX with a strong safety record.
Boeing said it was ready to assist China Eastern and was in contact with U.S. transportation safety regulators over the incident.
Chinese media carried brief highway video footage from a vehicle's dashcam apparently showing a jet diving to the ground behind trees at an angle of about 35 degrees off vertical. Reuters could not immediately verify the footage.
Flight MU5735 was en route from the southwestern city of Kunming, capital of Yunnan province, to Guangzhou, capital of Guangdong, bordering Hong Kong, when it crashed.
China Eastern said the cause of the crash was under investigation. Such accidents typically involve multiple factors and experts warned it was far too early to draw any conclusions on the potential causes, especially in light of the scarce information available.
Investigators will be scouring the wreckage and flight recorders for factors that could have caused the plane to plummet vertically and slam into the mountains at high speed.
The airline said it had sent a working group to the site. There were no foreigners on the flight, Chinese state television reported, citing China Eastern.
Relatives, friends and colleagues of passengers gathered late on Monday in a cordoned off area at the jet's destination, Guangzhou Baiyun International Airport.
One man surnamed Yan said that a colleague had been on the plane, and that he had notified the 29-year-old's mother.
"When she picked up the phone, she choked up," said Yan, adding that he had a "heavy heart" when he heard the news.
China Eastern staff were making arrangements for relatives who wished to travel to the crash site on Tuesday, Yan said. Reuters was not able to independently verify Yan's identity.
The aircraft, with 123 passengers and nine crew on board, lost contact over the city of Wuzhou, China's Civil Aviation Administration of China (CAAC) and the airline said.
The flight left Kunming at 1:11 p.m. (0511 GMT), FlightRadar24 data showed, and had been due to land in Guangzhou at 3:05 p.m. (0705 GMT).
The plane, which the flight tracking service said was six years old, had been cruising at 29,100 feet at 0620 GMT. The same flight number a day earlier began a normal gradual descent from the same altitude, also at 0620 GMT, and landed safely in Guangzhou, according to Flightradar24.
The flight that crashed instead began a rapid descent to 7,425 feet before recovering briefly to 8,600 feet and then descended rapidly again, FlightRadar24 data showed. The last tracked altitude was 3,225 feet above sea level.
Media cited a rescue official as saying the plane had disintegrated and caused a fire destroying bamboo trees. The People's Daily quoted a provincial firefighting department official as saying there was no sign of life among the debris.
State media showed a piece of the plane on a scarred, earthen hillside. There was no sign of a fire or personal belongings.
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.
Boeing said last year 13% of fatal commercial accidents globally between 2011 and 2020 occurred during the cruise phase, whereas 3% occurred on descent, none on initial approach, 28% on final approach and 26% on landing.
Online weather data showed partly cloudy conditions with good visibility in Wuzhou at the time of the crash.
President Xi Jinping called for investigators to determine the cause of the crash as soon as possible, state broadcaster CCTV reported.
Boeing said in a statement that its thoughts were with the passengers and crew.
"Boeing is in contact with the U.S. National Transportation Safety Board (NTSB) and our technical experts are prepared to assist with the investigation led by (CAAC)," the company said.
The disaster comes as Boeing seeks to rebound from several overlapping crises including the coronavirus pandemic and crashes involving its 737 MAX model. Shares of the planemaker closed 3.6% lower.
China Eastern has grounded its fleet of 737-800 planes, state media reported. It has 109 of the aircraft, according to FlightRadar24.
Shares of China Eastern Airlines in Hong Kong closed down 6.5% after news of the crash emerged, while its U.S.-listed shares closed 6.3%.
Aviation data provider OAG said this month that state-owned China Eastern Airlines was the world's sixth-largest carrier by scheduled weekly seat capacity.
The 737-800 has a good safety record and is the predecessor to the 737 MAX model that has been grounded in China for more than three years after fatal crashes in Indonesia and Ethiopia.
The crash has again thrust the U.S. manufacturer's most sold aircraft family into the spotlight and comes as it works to emerge from the 737 MAX safety crisis and global pandemic, which decimated air travel demand and strained its finances.
Investigators will search for the plane's black boxes - the flight data recorder and cockpit voice recorder - to shed light on the crash.
The U.S. NTSB said it had appointed a senior air safety investigator as an accredited U.S. representative to China's probe.
Air crash investigations are typically led by the country of the accident and include participation by the plane's country of origin, so U.S. investigators would be expected to join the probe of the U.S.-made Boeing jet.
China's airline safety record has been among the best in the world for a decade, although it is less transparent than in countries like the U.S. and Australia where regulators release detailed reports on non-fatal incidents, according to Greg Waldron, Asia managing editor at industry publication Flightglobal.