Air Canada will start suspending flights on Thursday after its unionized flight attendants served a notice to strike early Wednesday morning.

The airline on Wednesday said it will begin a phased winding down of most Air Canada and Air Canada Rouge operations over the next three days, with the first flights to be cancelled on Thursday, more on Friday and a complete cessation of flying on Saturday.

Just before 1 a.m. on Wednesday, the Canadian Union of Public Employees (CUPE), which represents 10,000 flight attendants at Air Canada and Air Canada Rouge, gave the airline notice that it intends to begin a strike.

“Air Canada has been forced into this decision to lock out its flight attendants and regrets the impact the suspension of operations will have on customers as a result of the union’s issuance of a strike notice during such a heavy travel period,” the company said in a release.

Air Canada said customers whose flights are cancelled will be notified and can obtain a full refund online through its website or mobile app. It also said customers without confirmed flights should not go to the airport.

Air Canada and Air Canada Rouge carry approximately 130,000 customers a day who could be affected by a disruption. This includes the 25,000 Canadians the airline flies home from abroad each day.

The carrier said it issued the union a statutory 72-hour lockout notice to mitigate the strike’s customer impact and allow for an orderly shutdown.

It said a controlled wind down allows it to advise customers in advance, reducing the chance of customers being stranded and giving the airline and customers time to make alternative travel arrangements.

“We regret the impact a disruption will have on our customers, our stakeholders and the communities we serve,” chief executive Michael Rousseau said in a statement. “As we have seen elsewhere in our industry with other labour disruptions, unplanned or uncontrolled shutdowns, such as we are now at risk of through a strike, can create chaos for travellers that is far, far worse.”

Air Canada said an unplanned shutdown is also a major risk for the company and its other employees. But it also said that by optimally positioning aircraft and crews ahead of a possible stoppage, it will be able to provide required routine maintenance and more quickly restore regular service.

The company said it has made arrangements with other Canadian and foreign carriers to provide customers alternative travel options, which they will be notified of if identified.

However, it said that securing such capacity in many cases will not be immediately possible, given that other carriers are already very full due to the summer travel peak.

Air Canada said it has also implemented a flexible rebooking policy for all customers, so they can change or defer travel at no additional cost.

The airline will inform passengers of their rights under applicable rules if their flight is cancelled or delayed and meet its regulatory obligations, it said.

The Canadian Federation of Independent Business (CFIB) said Air Canada and the union should resolve their issues with no disruption to service, pointing out that one-third of Canadian small companies depend on the summer tourism season for their revenues.

“Given the ongoing tariff disputes with the United States and China, Canadian businesses are scrambling to find new suppliers and customers in other provinces or other countries,” Corinne Pohlmann, CFIB’s executive vice-president, advocacy, said. “Removing Canada’s major domestic and international carrier from service would be another blow at this critical time.”

But Air Canada and CUPE have failed to reach a tentative agreement following eight months of negotiations.

The airline on Tuesday afternoon said negotiations with the union had

“reached an impasse” after it rejected an offer by the company to enter binding, third-party arbitration.

The union said Air Canada’s latest response made it clear that it is not interested in resolving employees’ issues.

A strike will commence just after midnight on Saturday, CUPE said in its strike notice addressed to Rousseau and federal mediator Peter Simpson.

“Regrettably, the company ceased to engage in meaningful dialogue on these critical issues, leaving us with no choice but to move forward in a manner that may impact the travel plans and long-anticipated vacations of the public. We do not take this lightly,” Wesley Lesosky, president of the Air Canada component of CUPE, said in the notice.

Rousseau said the “disappointing conduct” of CUPE’s negotiators and the union’s intention to launch a strike leaves the company’s only course of action to provide certainty by implementing an orderly suspension of operations.

In its update to members, CUPE said the decision was not made lightly, but was necessary after negotiators reached an impasse despite bringing in federal conciliators.

“We continued to bargain, putting forward solid, data-driven proposals on wages, expenses and unpaid work, all rooted in fairness and industry standards,” it said.

The airline said it has requested immediate intervention by the Canadian government to use its powers to direct binding interest arbitration under Section 107 of the Canada Labour Code before a work stoppage becomes effective.

Recent government interventions in rail, port and airline labour disruptions in Canada provide a proven precedent, the airline said.

In response, CUPE said it is calling on the Liberal government to “respect our right to take job action in pursuit of a fair contract.”

“Air Canada is clearly banking on the federal government bailing them out by pre-empting flight attendants’ charter-protected right to take job action,” it said.

The airline operates globally to approximately 65 countries on six continents with a fleet of 259 aircraft.

Air Canada Express flights operated by Jazz and PAL Airlines, which carry about 20 per cent of Air Canada’s daily customers, will continue to operate as normal.