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WestJet says it has started the process of parking 737 aircraft ahead of a possible labour disruption.Amir Salehi/The Globe and Mail

WestJet said on Friday it has started the process of parking 737 aircraft, as negotiations with flight attendants have not resulted in an agreement, which could lead to labour disruptions.

The Canadian Union of Public Employees, which represents 4,400 flight attendants at WestJet, triggered a 72-hour strike notice that ends on Sunday just after midnight in Calgary, where the airline is headquartered.

WestJet responded with a lockout notice on the same timeline.

WestJet flight attendants’ union issues 72-hour strike notice

Explainer: Why and when WestJet flight attendants could strike, and how it may affect you

The company has not disclosed how many flights it has cancelled in anticipation of a strike or lockout, but airlines typically begin to wind down flight schedules ahead of a labour deadline to avoid stranded crews and aircraft.

“This necessary step allows the airline to maintain operational control and protect the integrity of the broader network,” the airline said in a statement on Friday. “Most importantly, this proactive measure minimizes the risk of stranding guests and aircraft. ”

The airline has informed passengers travelling between July 30 and Aug. 4 that they can make a one-time change or cancellation at no additional cost. WestJet is also making preparations to operate on a reduced schedule, although the airline did not specify if or when it will start cancelling flights.