CALGARY, Alberta (AP) — Canada’s second largest airline, WestJet, has started to cancel flights because its talks with a pilots’ union are at an impasse, the carrier said Thursday, jeopardising travel plans for thousands of passengers ahead of a holiday weekend in Canada.

Some 1,800 pilots at the carrier and its Swoop subsidiary are poised to walk off the job overnight after the Air Line Pilots Association issued a strike notice earlier this week. Next Monday is Canada's Victoria Day federal holiday.

The Calgary, Alberta-based airline flies to more than 110 destinations including in the United States, Central America, the Caribbean, Europe and Asia. It has a fleet of more than 180 aircraft. With more than 4,000 flights scheduled over the next seven days, WestJet carries 28 per cent of Canada’s domestic market, while Air Canada carries 47 per cent, according to aviation data firm Cirium.

WestJet CEO Alexis von Hoensbroech said in the statement early Thursday that negotiations with the union were in a stalemate, leaving the company "with no choice but to begin taking the painful steps of preparing for the reality of a work stoppage.”

WestJet has begun to park the bulk of its fleet — 105 narrow-body 737s and seven wide-body 787 Dreamliners — using a “measured, phased and safe approach,” the statement read.

As of Thursday morning, the carrier had cancelled 92 flights or 17 per cent for that day, the aviation data firm’s figures show. Few flight cancellations had registered for Friday and afterward. But passengers are now unable to make online bookings for flights on major routes such as Calgary-Vancouver and Toronto-Calgary until Tuesday.

The federal labour minister and the government’s head mediator as well as WestJet’s CEO and the pilots’ union leaders have all descended on a hotel near the Toronto airport to work toward a deal.

Bernard Lewall, who heads the union’s WestJet contingent, says the workers’ issues revolve around pay, job security and scheduling, with pilots earning roughly half of what some of their US counterparts make.

The company said Thursday the union’s wage expectations were “unreasonable” and would “permanently damage the financial viability of the group’s future.”

The airline has advised travelers to check the status of their flight before leaving for the airport, and to visit WestJet’s guest updates webpage or Swoop’s website for more information on flight status and travel changes.