Air Transat, one of Canada's largest airlines, said it will start gradually suspending some flights starting on Monday ahead of a planned strike.

The union representing the airline's pilots issued a 72-hour strike notice on Sunday, announcing that Air Transat pilots will stop showing up to work on Wednesday if a contract agreement is not reached.

Following the strike notice, the airline said it would gradually shut down its operations "to prevent the consequences of a sudden, unplanned interruption".

The airline called the strike notice "premature" while a union leader said there is still time to avoid the strike.

"No pilot wants to strike, but Air Transat management has left us no choice," Capt Bradley Small, who heads a group of pilots within the union, said in a statement.

"Months of unproductive bargaining ends now. If we cannot reach an agreement, management will be responsible for every cancelled flight and stranded passenger."

Air Transat pilots have been negotiating for nearly a year to replace their current 2015 contract with one that they hope will cement "industry-standard pay, benefits, work rules, and job security", the pilots' union, the Air Line Pilots Association, said.

The union said that 99% of its 750 Air Transat pilots had voted to authorise their leadership to declare a strike.

In response, the airline - which is one of the three largest in Canada - said it will start cancelling flights on Monday, with a suspension of all flights on Tuesday, in preparation for a possible pilots strike on Wednesday.

"This strike notice is premature given the progress made at the bargaining table and the generous offers made by Air Transat," Julie Lamontagne, a human resources officer at Air Transat, said in a statement.

Ms Lamontagne said the airline had been negotiating in good faith, and accused the pilots union of showing "indifference toward Transat" in its "reckless decision" to authorise a strike "that does not reflect the state of negotiations".

The airline said it its flight cancellations were necessary to prevent crews, passengers and aircraft from being "stranded abroad if the strike occurs".

In 2024, Air Transat's flight dispatchers overwhelmingly voted to approve a strike after contract negotiations with their union stalled, but that strike was ultimately averted.