Air Canada's labor dispute deepened Sunday as the Canadian Union of Public Employees (CUPE) declared flight attendants would continue striking, openly defying a Canada Industrial Relations Board (CIRB) order to return to work by 2 p.m. Eastern Time. The walkout, involving more than 10,000 employees, has forced the country's largest airline to suspend operations and disrupted travel for more than 100,000 passengers a day at the peak of the summer season.

Air Canada said it had planned to resume flights Sunday evening after the federal government intervened. But the carrier announced late Sunday it would now delay restarting operations until Monday evening. "The union illegally directed its flight attendant members to defy a direction from the Canadian Industrial Relations Board," the airline said in a statement.

CUPE called the board's order unconstitutional and accused Air Canada of exploiting government intervention to avoid serious negotiations. "Our members are not going back to work," Mark Hancock, CUPE's national president, told reporters outside Toronto's Pearson International Airport. "We are saying no."

The conflict stems from stalled contract talks over pay and compensation for time spent on the ground. Flight attendants say they are largely paid only when planes are moving and demand recognition for unpaid duties such as boarding and layovers. Air Canada countered that its latest offer, including a 38% increase in total compensation over four years, would have made its flight attendants the best compensated in Canada. The union rejected the proposal, saying the proposed 8% first-year raise was inadequate given inflation.

The CIRB's order followed a request from Prime Minister Mark Carney's government to impose binding arbitration, citing the need to protect the economy. Federal Jobs Minister Patty Hajdu underscored the urgency of preventing prolonged disruption, warning that "now is not the time to take risks with the economy."

The strike has already forced the cancellation of around 700 flights daily and stranded passengers worldwide. Travelers at Toronto Pearson International Airport reported confusion over alternative arrangements. "We are kind of left to figure it out for ourselves and fend for ourselves with no recourse or options provided by Air Canada at this time," said Elizabeth Fourney, a passenger from Vancouver.

Air Canada said it would provide full refunds and seek to rebook passengers on other airlines when possible, though it cautioned that high demand during peak season limited availability. The carrier also confirmed that the CIRB had extended the terms of its expired March 31 collective agreement until a new deal is reached.

Union leaders accused the CIRB of bias, citing the board chair's previous role as Air Canada's legal counsel. It is a "staggering conflict of interest," the union said, arguing the ruling was tainted. Other labor groups joined the flight attendants' picket lines Sunday in solidarity. "They are in support here today because they are seeing our rights being eroded," said Natasha Stea, a Toronto-based flight attendant and local union president.