The union representing 10,000 Air Canada flight attendants said it will challenge an order to return to work and remain on strike.

Air Canada is bracing for one of its most significant labor disruptions in recent history, announcing it expects to cancel several dozen flights by Thursday night and around 500 flights by the end of Friday.

A walkout by flight attendants ended after about 12 hours with the imposition of binding arbitration. But getting travel back to normal will take days.