Flight MU5735, operated by China Eastern Airlines, was en route between the two southern cities of Kunming and Guangzhou when, at around 2:20 p.m. China time, the aircraft plunged into a precipitous descent.

Without access to data stored onboard the plane’s so-called black box recorders, investigators can’t determine exactly how or why the jet crashed. But preliminary data from flight tracker website Flightradar24 indicates that, at about 100 miles from its destination and just as the Boeing 737 should have begun a controlled descent, the aircraft lurched into a nosedive, plummeting from its cruising altitude of 29,100 feet to 3,225 feet, its last known signal, in just over a minute and a half.

Flightradar24 data suggests flight MU5735 hurtled toward earth at a rate of over 30,000 feet per minute. In a still unexplained twist, Flightradar24’s data shows that, after falling for over 40 seconds, the plane halted its nosedive and began to climb again, regaining 1,000 feet in roughly 10 seconds, before plunging once more.

Forces created by the plane’s whipsaw trajectory would have thrown passengers first to the ceiling and then pinned them to their seats, as the Boeing 737 snapped from a steep nosedive to an abrupt ascent.

Surveillance footage from a mine nearby the crash site appears to show flight MU5735 in a near-vertical nosedive before the moment of impact. Chinese digital news site The Paper has confirmed the footage—shared on social media—was captured by the mine’s CCTV cameras, but the image is too blurry to verify that the object in the shot is flight MU5735.

Flight safety experts say it is too early to speculate on what caused the crash, but China Eastern has grounded all other flights aboard Boeing 737-800 models, leaving 100 aircraft stuck on the tarmac.

A wider ban on the aircraft seems unlikely. The Boeing 737-800 is one of the Chicago-based planemaker’s safest models, in terms of its flight-to-crash ratio, and is different from the 737 Max that was at the center of a major safety scandal three years ago.

The 737 Max scandal erupted in March 2019 when global flight regulators grounded all 387 Max aircraft in operation following two fatal crashes that appeared to have been caused by a fault in the 737 Max’s autopilot software. The software forced the planes into unintended nosedives.

Boeing’s stock has never fully recovered from the fallout of that scandal—its share price plunged 18% in March 2019, when regulators began grounding 737 Max models, hitting $362 from a high of $440.

During the onset of the pandemic in 2020, Boeing’s stock took an even deeper dive, plunging to a low of $95 per share. After dropping 7% on news of the crash on Monday, Boeing shares are now trading at $185.90.

Boeing has gradually repaired its reputation since the 737 Max scandal and resumed sales of the new jet. But China was the last of the planemaker’s major customers to accept deliveries of the 737 Max. Beijing only lifted its ban on 737 Max purchases in December last year, and Boeing delivered its first 737 Max to the country just last week.

Monday’s plane crash might have placed a pause on Boeing’s rehabilitation in China, but the group says it is “working with our airline customers and are ready to support them” in the wake of the incident.