China Eastern flight 5735 displayed "unusual" flight patterns before it crashed into a mountainous region in southern China, aviation experts say.
The Boeing 737-800 was carrying 132 people as it made its way to the industrial centre of Guangzhou along the east coast, after taking off from Kunming in the southwestern province of Yunnan.
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Around 2.20pm local time the plane entered a steep dive at a speed of 842kp/h from an altitude of around 9144 metres.
Just over 90 seconds later it crashed near the city of Wuzhou in the Guangxi region.
READ MORE: Chinese airliner crashes with 132 aboard in country's south
While it's too early to know what caused the crash, president and CEO of Flight Safety Foundation Dr Hassan Shahidi said it's "unusual".
"From the time of the descent to the crash, it took under two minutes. This is very unusual and this is known as loss of control in flight," he told Today.
"It was cruising at about 29,000ft before it began to descend rapidly. It lost 21,000ft in about 70 seconds.
"It stopped descent at about 7400ft and briefly climbed to about 8600ft before it began to descend again."
Aviation expert Neil Hansford from Port Stephens, New South Wales said the near-vertical angle of the crash provided a clue as to what could have happened.
"It has just dropped like a rock, if there's a problem in the cruise the aircraft would have a bit of a trajectory at an angle going down," he said.
"This has gone straight down. It's likely when you go through the causes it has been hit in flight with military ordinance or there's been a pilot intervention or a collision.
"It is unlikely, unless it was absolutely catastrophic like the wings falling off, for it to have fallen from the sky in the way that it did."
More than seven hours after the crash there is still no word of survivors.
Rescuers have begun the hard task of navigating the steep terrain, but it was local villagers who first arrived on the scene.
The plane crash sparked a wildfire so fierce it was visible from space.
Dr Shahidi said two things are now needed for air crash investigators; the flight data recorder and the voice data recorder.
"The sooner those flight recorders are found, the sooner that we will find out exactly what happened," he said.
"They will be looking at the aircraft history certainly, which is actually very new, seven years old.
"We will be looking to the maintenance history of this aircraft well as the engines. They will be looking to structural issues or aspects of this aircraft and certainly the investigator also be looking into pilot proficiency and training."
Dr Shahidi said he did not want to speculate about the cause of the crash until more is known.
But he insisted the Boeing 737 800 is safe.
"It has been around for many decades," he said.
"There are roughly 4200 of these around the world. About 1,100 in China. It has had a very good safety record over the decades.
"I am not concerned about generally the safety record of this aircraft."
A later version of the passenger jet, the 737 Max, was grounded worldwide for nearly two years after two crashes in 2018 and 2019 killed 346 people.
Lion Air flight 610 and Ethiopian Airlines flight 302 crashed less than five months apart.
Investigators tied an issue with the plane's MCAS, or Maneuvering Characteristics Augmentation System, to both crashes.
- WITH AP
