Air India, which is part of the global Star Alliance of airlines, had decided to ramp up operations on Sunday.

Air Canada operates 130,000 daily passengers and flies directly to 180 cities worldwide.

Meanwhile, the union representing Air Canada flight attendants has said its workers remain on strike, defying the back-to-work order.

The Canadian Union of Public Employees says it will challenge an order by the Canada Industrial Relations Board to return to work by 2 p.m. ET, The Canadian Press reported.

In a statement, Air Canada said it suspended its plan to resume limited flying by Air Canada and Air Canada Rouge after the Canadian Union of Public Employees (CUPE) 'illegally' directed its flight attendant members to defy a direction from the Canadian Industrial Relations Board (CIRB) to return to work.

"Approximately 240 flights scheduled to operate beginning this afternoon have now been cancelled. Typically, the carriers operate 700 flights a day," the statement said.

Meanwhile, CUPE has reportedly invited Air Canada to the negotiation table.

In addition to wage increases, the union says it wants to address uncompensated ground work, including during the boarding process.