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 says it will begin cancelling flights starting Thursday to allow an orderly shutdown of operations with a complete cessation of flights for the country’s largest airline by Saturday as it faces a potential work stoppage by its flight attendants.

The Canadian Union of Public Employees, representing more than 10,000 Air Canada cabin crew, on Wednesday gave the airline a 72-hour deadline to reach a pay deal or face strike, hours after the carrier asked sought federal government intervention.