The Montreal-based airline said labor negotiations with its 10,000 flight attendants are at an impasse and warned that the carrier may begin to shut down operations as early as Saturday without an agreement.

Air Canada said on Tuesday it has asked the federal government for a referral to binding arbitration on its contract talks with the flight attendants union, after the airline declared an impasse in the negotiations.

There’s no word yet whether Air Canada and the union representing some 10,000 of its flight attendants have averted a possible strike or lockout that could begin as soon as Saturday.