Canada’s Industrial Relations Board (CIRB) has declared Air Canada’s strike by 10,000 cabin crew members illegal after workers ignored a Sunday return-to-work order. The crew is striking over wages, citing inflation and lack of pay for ground duties like boarding assistance, Al Jazeera reported.

Mark Hancock, president of the Canadian Union of Public Employees (CUPE), the union representing the crew, said he is willing to face jail or fines rather than end the strike. Air Canada CEO Michael Rousseau said the union’s demands exceed the airline’s 40 percent offer.

Prime Minister Mark Carney urged a resolution to reduce travel disruption. Air Canada has suspended its profit forecasts, while the union continues to call for negotiations toward a “fair deal”, according to Al Jazeera.