Air Canada expects to cancel the majority of its flights by day's end and around 500 flights by the end of the week, ahead of a planned weekend strike by its unionized flight attendants, leaving some 100,000 passengers scrambling to make alternative travel plans.

Canada's largest carrier said on Thursday it would cancel several dozen flights by day's end and around 500 flights by the end of Friday, as its 10,000 flight attendants gear up to strike over stalled contract talks on higher wages and unpaid work.

Mark Nasr, chief operations officer at Air Canada, said the complexity of the carrier's network, which operates over 250 aircraft on flights to over 65 countries, requires it to start winding down service now. Restarting operations would take a week to complete.

"It's simply not the kind of system that we can start or stop at the push of a button," Nasr told reporters in Toronto.

FlightAware data shows Air Canada has, thus far, cancelled nine flights as of midday.

A strike would displace passengers, hit the country's tourism sector during the height of summer travel, and pose a fresh test for the ruling Liberal government under Canadian Prime Minister Mark Carney, which has been asked by the carrier to intervene and impose arbitration.

Air Canada and low-cost carrier Air Canada Rouge carry about 130,000 customers a day. Air Canada is also the foreign carrier with the largest number of flights to the US.

US carrier United Airlines, a code share partner of Air Canada, said it has issued a travel waiver to help customers manage their travel plans.

Passengers expressed concerns over missed vacations and getting stranded abroad due to the looming strike, but also voiced support for flight attendants.

David Nguyen, 28, a pharmacist who is currently on vacation outside of Cancun, Mexico, said he is worried his flight back to Toronto will get cancelled, leaving him stranded in paradise. He said he tried rebooking on another carrier but all the refundable options are sold out and the ones that are left are over $1000 (US$724.06).

“If my flight does get cancelled, I think that's where I'll be in a little bit of a pickle because I don't really know what my next step will be,” said Nguyen.

He added that Air Canada "should just pay their flight attendants appropriately."

Summer Mehdi, 19, a third-year college student at Queen's University said her family of four planned to catch a flight from Toronto to Lisbon on the weekend, but their summer vacation to Portugal and France is now in limbo.

"My family and I, we 100 per cent agree with the strike happening and we obviously want the employees to get what they deserve," Mehdi said. "We just wish there was more communication and I think it's just like a stressful situation for everyone."

Unpaid work

Earlier in the day, Canadian Jobs Minister Patty Hajdu urged the country's largest carrier and union to return to the bargaining table to reach a deal that could avert disruptions.

A spokesperson for the Canadian Union of Public Employees, which represents the carrier's 10,000 flight attendants, said Air Canada negotiators are not bargaining and have not responded to a proposal they made earlier this week.

"We believe the company wants the federal government to intervene and bail them out."

CUPE has previously said it opposes binding arbitration.

Arielle Meloul-Wechsler, chief human resources officer at Air Canada, said the carrier is "still available to bargain at any time on the condition that the negotiation has substance."

Air Canada executives speaking at a press conference ended it abruptly due to protests by union members donning placards.

The dispute hinges on the way airlines compensate flight attendants. Most airlines have traditionally paid attendants only when planes are in motion.

But in their latest contract negotiations, flight attendants in North America have sought compensation for hours worked, including for tasks like boarding passengers and waiting around the airport before and between flights.

The union said Air Canada had offered to begin compensating flight attendants for some unpaid work but only at 50 per cent of their hourly rate.

The airline said it had offered a 38 per cent increase in total compensation for flight attendants over four years, with a 25 per cent raise in the first year.