The union representing WestJet pilots voted overwhelmingly in favour of a strike mandate Tuesday, casting clouds of uncertainty over Canadians' travel plans.

The Air Line Pilots Association said its 1,600 WestJet pilots can launch a strike as early as May 16 — the Tuesday ahead of the May long weekend, which typically kicks off the summer travel season for thousands whose itineraries could now be upended.

The workers' issues revolve around job protection, pay and scheduling at the airline and its discount subsidiary Swoop, said Bernard Lewall, who heads the union's WestJet contingent.

"If you're trying to attract new pilots or retain the experienced ones that we have, there's got to be some definition of a career path for them. And because there's three different airlines under the umbrella of WestJet flying the same airplanes, all with different wages and working conditions, there really isn't that defined career path," he said in a phone interview from Calgary.

"It is no longer a career destination."

Some 240 pilots left the carrier last year, followed by about 100 so far this year, most of them to other airlines, he said.

Around 95 per cent of pilots took part in the strike vote, with 93 per cent of them in favour of the mandate.

Pilots could also opt for more restrained job action such as refusal to work overtime, Lewall noted.  

WestJet chief operating officer Diederik Pen said in a statement that strike authorization is a "common step" by unions during labour negotiations and "does not mean a strike will occur."

WestJet CEO Alexis von Hoensbroech told reporters last Wednesday that bookings were not being affected by the threat of a strike and that he expects to resolve the standoff.

"Recruitment is actually running pretty well," he said in a phone interview from Calgary last Thursday, referring to pilots. "But what we are seeing is high attrition. That's certainly an impact of the current situation."

Resignations have been especially frequent at WestJet Encore, the carrier's regional subsidiary, "which is actually pretty painful, although they're not subject to the current bargaining," von Hoensbroech said.

"Some of them are being actively recruited by some competitors."

Von Hoensbroech, who has headed the Calgary-based airline since February 2022, said he expects to get through negotiations without any job action and with "meaningful improvements to their contract."

Lewall is calling for a "North American standard contract," but von Hoensbroech suggested that asking for pay on par with U.S. counterparts is far-fetched.

"Pilots dream about U.S. wages. The union keeps on repeating that all they want is a standard North American contract," the CEO said. 

"But the U.S. is a totally different market on the aviation side," he continued.  "If you want the wages of another country, then you move to this other country and then live with everything it comes with."

Talks are ongoing through the federal conciliation process, which will end April 24 followed by a three-week break, unless the parties agree to extend negotiations.

This report by The Canadian Press was first published April 18, 2023.

This is a corrected story. An earlier version incorrectly included a division of WestJet that is not involved in the strike vote.