WestJet is cancelling flights ahead of a possible strike by its mechanics' union.

The Calgary-based airline says in a statement the Aircraft Mechanics Fraternal Association has provided them with another notice of strike action.

WestJet says that as a result, it has preemptively cancelled 25 flights between Thursday and Friday, affecting about 3,300 customers.

This comes as the Aircraft Mechanics Fraternal Association is accusing WestJet of suing it without notifying its negotiators, who are working with the airline on working out a new collective bargaining deal.