Rescuers have not found any survivors among the scattered wreckage of a China Eastern plane carrying 132 people that crashed on Monday in a forested mountainous area in southern China.
"Wreckage of the plane was found at the scene, but up until now, none of those aboard the plane with whom contact was lost have been found," state broadcaster CCTV said on Tuesday morning, more than 18 hours after the crash.
Footage appeared to show the plane's last moments as it nosedived into a mountainous area in south China in the country's worst air disaster in nearly a decade.
"The plane fell vertically from the sky," state-run Beijing Youth Daily quoted a local resident as saying.
The crash ignited a fire big enough to be seen on NASA satellite images and created a deep crater in the hillside.
China Eastern Airlines flight MU5735, a Boeing 737-800, was en route from the south-western city of Kunming, the capital of Yunnan province, to Guangzhou, the capital of Guangdong, bordering Hong Kong, when it crashed.
The airline said it deeply mourned the passengers and crew, without specifying how many people were killed.
"Our thoughts are with the passengers and crew of China Eastern Airlines flight MU 5735," Boeing said in a short statement.
"We are working with our airline customers and are ready to support them."
While rescuers work to determine the number of people who died, 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.
Chrystal Zhang, an associate professor in aerospace engineering in RMIT, told the ABC the key to understanding the cause of the crash was recovering the plane's black box.
"The black box carries all the information: the flight data about the aircraft, the flight information, the communication between the air crew and ground air traffic controllers," she says.
Dr Zhang said until the black box was found, it was "very, very challenging to come to any kind of a conclusion".
"But having said that, there's some preliminary justifications in terms of understanding what exactly could and would possibly contribute to the causes of this air crash," she said.
"Generally speaking, we categorise air crashes into two broad categories: One is caused by human factors, that is referring to errors made by humans, which could be the air traffic controllers in terms of giving the wrong direction, or could be the pilots who press the wrong button or not functioning properly in front of the control board, or the mechanics who fail to do the proper checks.
"The other major contributing factor could be mechanical issues.That could be the failure of the engines, the failure of the mechanical issues or the technical issues.
The aircraft lost contact over the city of Wuzhou, China's Civil Aviation Administration of China (CAAC) and the airline said.
The flight left Kunming at 1:11pm local time, FlightRadar24 data showed, and was due to land in Guangzhou at 3:05 pm local time.
The plane, which Flightradar24 said was six years old, had been cruising at 29,100 feet at 2:20pm local time. It then began a rapid descent to 7,425 feet before recovering to 8,600 feet and then descended rapidly again.
The last tracked altitude was 3,225 feet above sea level.
China's President Xi Jinping called for investigators to determine the cause of the crash as soon as possible, state broadcaster CCTV reported.
Boeing chief executive Dave Calhoun said the aerospace company had offered the full support of its technical experts in the investigation of the crash.
In an email sent to employees, Mr Calhoun said he was limited by what Boeing could say about the investigation being led by the Civil Aviation Administration of China (CAAC).
"Trust that we will be doing everything we can to support our customer and the accident investigation during this difficult time, guided by our commitment to safety, transparency, and integrity at every step," Mr Calhoun wrote.
Crashes during the cruise phase of flights are relatively rare, even though this period accounts for the majority of flight time.
Boeing said last year only 13 per cent of fatal commercial accidents globally between 2011 and 2020 occurred during the cruise phase, whereas 28 per cent occurred on final approach and 26 per cent on landing.
"Usually the plane is on autopilot during cruise stage so it is very hard to fathom what happened," Li Xiaojin, a Chinese aviation expert, said.
Plane predecessor to 737 MAX
Online weather data showed partly cloudy conditions with good visibility in Wuzhou at the time of the crash.
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 Australia and the US where regulators release detailed reports on non-fatal incidents, according to Greg Waldron, Asia managing editor at industry publication Flightglobal.
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 following fatal crashes in Indonesia and Ethiopia.
"There were a few years, particularly in 1994, 2003 and 2004, where there were some air crashes [in China's aviation industry] causing a lot of casualties," Dr Zhang said.
"But after that the government, the industry, the community, have made significant efforts in terms of enhancing the safety record of the overall aviation sector."
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 a colleague had been on the plane, and 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 Australian Department of Foreign Affairs is investigating whether any Australians were on board the flight.
"Australian representatives in China are making urgent enquiries with the airline and local authorities to ascertain whether any Australians were on board," it said in a statement.
ABC/wires
