India, Aug. 18 -- Hundreds of Air Canada planes remained grounded on Monday with striking flight attendants defying government-backed orders to return to work, disrupting travel plans for passengers.

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.

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.

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