Air Canada said it suspended plans to restart operations on Sunday after the union representing 10,000 flight attendants said it will defy a return to work order. The strike was already affecting about 130,000 travelers around the world per day during the peak summer travel season.

The Canada Industrial Relations Board ordered airline staff back to work by Sunday afternoon after the government intervened and Air Canada said it planned to resume flights Sunday evening.

Canada’s largest airline now says it will resume flights Monday evening. Air Canada said in a statement that the union “illegally directed its flight attendant members to defy a direction from the Canadian Industrial Relations Board.”

“Our members are not going back to work,” Canadian Union of Public Employees national president Mark Hancock said outside Toronto's Pearson International Airport. “We are saying no.”

Hancock ripped up a copy of the back-to-work order outside the airport’s departures terminal where union members were picketing Sunday morning. He said they won't return Tuesday either.

Flight attendants in Vancouver chanted "unpaid work, won't fly."

“Like many Canadians, the Minister is monitoring this situation closely. The Canada Industrial Relations Board is an independent tribunal," Jennifer Kozelj, a spokeswoman for Federal Jobs Minister Patty Hajdu said in a emailed statement.

Hancock said the “whole process has been unfair” and said the union will challenge what it called an unconstitutional order.

Less than 12 hours after workers walked off the job, Hajdu ordered the 10,000 flight attendants back to work, saying now is not the time to take risks with the economy and noting the unprecedented tariffs the U.S. has imposed on Canada. Hajdu referred the work stoppage to the Canada Industrial Relations Board.

The airline said the CIRB has extended the term of the existing collective agreement until a new one is determined by the arbitrator.

The shutdown of Canada’s largest airline early Saturday was impacting about 130,000 people a day. Air Canada operates around 700 flights per day.

“Like many Canadians, the Minister is monitoring this situation closely. The Canada Industrial Relations Board is an independent tribunal," Jennifer Kozelj, a spokeswoman for Federal Jobs Minister Patty Hajdu said in a emailed statement.

Hancock said the “whole process has been unfair” and said the union will challenge what it called an unconstitutional order.

Less than 12 hours after workers walked off the job,)Hajdu ordered the 10,000 flight attendants back to work, saying now is not the time to take risks with the economy and noting the unprecedented tariffs the U.S. has imposed on Canada. Hajdu referred the work stoppage to the Canada Industrial Relations Board.

Jenny Phelps, from Vancouver, was just one of the passengers who found herself grounded in Ottawa.

"I came with my family here for a family vacation. And now we can't get home," she said.

Another passenger, Andrew Dixon, was also trying to get back to the United Kingdom.

"I'm trying to get back home to London. Hopefully, I'm going to get back. But we'll see, I guess," he said.