Witnesses and video from the scene Monday afternoon shows the plane landing so hard that its right wing is sheared off. It bursts into flames before sliding down the runway and flipping over. Miraculously, all 80 people on board the flight from Minneapolis to Toronto’s Pearson International Airport survived.

“It appears from the video that the plane landed so hard that the right main gear collapsed. The tail and right wing began skidding causing the plane to roll over to the right,” Ella Atkins, the head of Virginia Tech’s aerospace and ocean engineering department and a pilot. “During the rollover, the right wing and tail sheared off, and a fire ignited, likely due to skidding and fuel leakage at least from a right wing tank.”

All but two of the 21 people injured on the flight have been released from hospitals, the airport CEO said Tuesday.

”How grateful we are there was no loss of life or life threatening injuries,” Deborah Flint, CEO of Greater Toronto Airports Authority, said during a news conference. “The crew heroically led passengers to safety.”

Crash investigation

Communications between the tower and pilot were normal on approach and it’s not clear what went wrong when the plane — a Mitsubishi CRJ-900 made by the Canadian company Bombardier — touched down.

Aviation experts said investigators will consider conditions on the ground, the pilot’s actions before landing, and potential problems with the landing gear. The Transportation Safety Board of Canada is leading the investigation with support from the U.S. National Transportation Safety Board.

Juan Browne, a commercial pilot who discusses aviation incidents on his popular YouTube channel, said preliminary data suggests the speed and rate of descent, crosswinds and the weather were “within limits.”

But Browne raised concerns about the pilots’ actions before landing.

“It appears that the aircraft simply did not flare at all,” Browne said. Flaring slows the aircraft’s rate of descent. “They just drove it into the runway.”

At the time of the crash, Pearson was experiencing blowing snow and winds of 32 mph (51 kph) gusting to 40 mph (65 kph), according to the Meteorological Service of Canada. The temperature was about 16.5 degrees Fahrenheit (minus 8.6 degrees Celsius). Browne said blowing snow reduces visibility.

Michael McCormick, an assistant professor and program coordinator for air traffic management at Embry-Riddle Aeronautical University in Daytona Beach, Florida, said investigators would look closely at the landing gear to make sure it was properly locked in place, and would consider staffing on the ground and in the aircraft.

“They will look at the number of people working both on the aircraft and the control towers. And they will look at their schedules,” McCormick said. “Are they well rested? Are they well staffed?”

But a Canadian investigator refused to comment on preliminary theories.

“At this point, it’s far too early to say what the cause of this accident might be,” TSB Senior Investigator Ken Webster said in a video statement Tuesday, as he stood near the remains of the aircraft.

He said investigators will examine the wreckage and runway, and have removed the cockpit voice and flight data recorders and sent them to the lab for analysis.

‘Everything just kind of went sideways’

Peter Carlson, who was traveling to Toronto for a paramedics conference, said the landing was “very forceful.”

“All the sudden everything just kind of went sideways and the next thing I know, it’s kind of a blink and I’m upside down still strapped in,” he told CBC News.

That everyone survived the Delta crash is a testament to the safety improvements made by airlines and aircraft manufacturers, including wings that are designed to come off to reduce explosions, well-trained flight crews and seats built to withstand impacts of up to 16 times the force of gravity.

“That seat is your single best resource in order to keep you protected,” McCormick said. “There’s a reason why the flight attendants walk around the aircraft prior to (landing) … to make sure everybody has their seat belts fastened.”

But is it safe to fly?

The crash was the fourth major aviation accident in North America in recent weeks. A commercial jetliner and an Army helicopter collided near Reagan National Airport in Washington, D.C., on Jan. 29, killing 67 people. A medical transportation plane crashed in Philadelphia on Jan. 31, killing the six people on board and another person on the ground. And on Feb. 6, 10 people were killed in a plane crash in Alaska.

Nevertheless, according to Jeff Guzzetti, an airline safety consultant and a former FAA and NTSB investigator, air travel is “extremely safe.”

“The odds of getting injured or killed in an commercial airline accident is far less than driving in your car,” Guzzetti said.

Still, he worries about layoffs at the Federal Aviation Administration under the Trump administration. ”I am concerned that the proposed cuts and changes to the FAA may increase the risk of further accidents,” he said.

The Delta flight was cleared to land at about 2:10 p.m. Audio recordings show the control tower warned the pilots of a possible air flow “bump” on approach.

“It was windy, but the airplanes are designed and certified to handle that,” said John Cox, CEO of aviation safety consulting firm Safety Operating Systems in St. Petersburg, Florida. “The pilots are trained and experienced to handle that.”

Carlson said when he took off his seat belt he crashed onto the ceiling, which had become the floor. He smelled gas, saw aviation fuel cascading down the cabin windows and knew they all had to get out. Carlson and another man assisted a mother and her son out of the plane, then Carlson dropped onto the snowy tarmac.

“All of us just wanted to be out of the aircraft,” he said.