TORONTO >> Investigators will consider the weather conditions, as well as the possibility of human error or an aircraft malfunction as they try to determine why a Delta Air Lines jet burst into flames and flipped upside down as it tried to land in Toronto, aviation experts said Tuesday.

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 fligh t 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.”

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. 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?”