Canada's largest airline said Toronto's Pearson International and Billy Bishop airports, Montreal's Trudeau International Airport and airports in Ottawa, St. John's, N.L. and Halifax were affected, as well as airports in Boston, Chicago, Cleveland, New York, Philadelphia and Washington.
Air Canada (TSX:AC.A) says passengers should check their flight status online before leaving for the airport and that those booked on affected flights will be able to rebook without penalty, space permitting.
The alert follows weather related problems earlier this week that caused backlogs and delays involving many airlines at Toronto's Pearson Airport.
Pearson spokeswoman Trish Krale says flight schedules were mostly back to normal Thursday, with roughly 40 flights cancelled — down from about 400 on Wednesday.
She said the airport continues to recover from the disruptive weather.
"There are still some things in the terminal that are having to be dealt with in terms of bags and rebooking people."
The delays were a result of extreme cold triggering a ground stop at the Toronto airport on Tuesday, which prevented North American flights from landing for more than eight hours.
The airport instituted the ground stop after Tuesday's wind chill readings hovered around the -40 C mark and more than 600 flights were cancelled during the day.
Airport officials said the ground stop was implemented because of how the cold was affecting equipment and to minimize time outdoors for employees.
Air Canada had advised travellers Wednesday that severe winter conditions in eastern Canada and the U.S. northeast were still impacting its operations.
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