Air Canada flight attendants are continuing their strike action in defiance of a government-backed labour board order mandating a return to work by 2 p.m. ET Sunday.

The Canadian Union of Public Employees (CUPE), representing over 10,000 striking attendants, called the order “unconstitutional” and has urged the airline to return to the bargaining table.

The walkout, which began Saturday, is already causing massive disruption during peak travel season, with more than 130,000 travelers impacted daily. Air Canada has announced it will attempt to resume some flights Monday evening.

On Saturday, the federal government intervened by requesting the Canada Industrial Relations Board (CIRB) to impose binding arbitration, a move permitted under the Canada Labour Code when the economy is deemed at risk. The CIRB complied, ordering the union back to work.

But in a rare act of defiance, the union has refused to comply, marking the first strike action by Air Canada flight attendants since 1985.

The government has yet to clarify what enforcement measures could follow if the union continues its illegal job action.

This standoff sets the stage for a high-stakes showdown between labour rights and federal authority, with major implications for both Canada’s aviation sector and broader labour relations landscape.