A Boeing 737 landed at Pearson International Airport shortly after sundown, ferrying 168 WestJet passengers from Cancun, Mexico. Outside, on an evening of record-setting cold in Toronto, workers were towing an empty Sunwing plane across the airfield.
Neither of the two airlines or Swissport, whose worker was towing the empty plane, have explained how it managed to hit the WestJet flight.
Many passengers have described what it felt like.
The plane was still waiting to park at 6:20 p.m., according to the airport. Passenger Stephen Belford wrote that the pilot had just announced there was staffing shortage over the intercom - and then came the jolt.
The empty plane - also a 737 - backed straight into the WestJet flight, the Canadian Broadcasting Corp. reported. "There was an audible crunch, and the plane rocked slightly," Gustavo Lobo told the outlet. "Everyone was a little shocked and kind of chuckling at the situation."
People watched as something started to spew out of one of the plane wings. "And then it set in that it's not steam, it's gas," a passenger told CTV News. "And then the whole thing ignites and everyone starts panicking."
"Big fire!" someone yells in a video from the WestJet flight.
People screamed, some thinking their own plane was on fire.
"Remain seated, remain seated, remain seated," someone urged, but not everyone listened. People stood in the aisle. A small girl stood up in her seat and wheeled around as flames shot off Sunwing's wing outside her window.
Seated with his wife and 12-year-old son, Ali Alagheband told CBC News, he managed to stay calm until black smoke began to fill the cabin.
"Oh, f- me," someone yelled in a video.
The conversation over air traffic control radio was calmer, but no less dire. "We're on fire," a pilot said in monotone, as reported by Global News. "Mayday, mayday, mayday. We're evacuating."
"Grab your jacket, guys," a man said in the video.
But even then, several passengers reported that the aisles were blocked by people searching for their overhead bags.
It was ridiculous," Alagheband told CBC News. "I was literally yelling, 'Get the F off the plane."
In the end everyone made it off. They slid out of the plane into subfreezing weather, onto an airfield that reeked of burned fumes.
About 15 minutes after the crash, WestJet tweeted: "Guests are safely in the terminal and they are in the process of clearing customs."
Emergency vehicles surrounded the planes, creating a spectacle at the gates. Firefighters extinguished the fire before it spread beyond the wing, but one was injured and taken to a hospital. An airport spokeswoman told The Washington Post the firefighter was later released and will recover.
Canada's Transportation Safety Board arrived after the fire and started interviewing passengers, a spokesman for the agency told The Washington Post. Investigators plan to speak with the flight crew and anyone else involved before releasing details about the collision.
Adrianna Lobo told CTV News she only began to comprehend the events after she and her children had escaped.
"I started crying because I realized what happened," she said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)