The Transportation Safety Board of Canada is investigating a near collision between a Porter Airlines plane arriving from Ottawa to Toronto's island airport and what appears to be either a drone or a balloon.
The Monday-morning incident, which involved Porter Flight 204, injured two cabin crew members after the pilot had to take evasive manoeuvres, said Julie Leroux, a TSB spokeswoman.
The plane, a twin-engined turboprop de Havilland Canada Dash 8, was approaching Billy Bishop Toronto City Airport around its scheduled landing time of 7:30 a.m.
There was a risk of a midair collision with an "unidentified object, likely an unmanned aerial vehicle," Ms. Leroux said.
A passenger, however, said the pilot thought it was a balloon.
At the time, the plane was at an altitude of 9,000 feet, about 30 nautical miles east of Toronto, on its approach to landing.
The passenger told The Globe and Mail that the pilot had just told the cabin crew to get ready for the descent when the aircraft went into a dive.
"All of a sudden, the plane dipped. Everyone yelled," said event planner Julia O'Grady, president of ITM Events. "It was a little bit scary."
She said the pilot made an announcement afterward, apologizing for the sudden manoeuvre and saying the crew had tried to avoid what looked like a balloon.
After landing in Toronto, Ms. O'Grady said, her next flight were delayed for an hour because the airline had to replace the two injured flight attendants.
The plane, which usually seats about 70 passengers, was almost full at the time of the incident, she said.
Ms. Leroux said the TSB has sent a team of investigators to the airport and the crew is to be interviewed in the afternoon. The plane is still at the airport.
Porter Airlines didn't immediately answer a request for comments.