TORONTO (AP) — More than 10,000 Air Canada flight attendants went on strike after a deadline to reach a deal passed, the union confirmed early Saturday. Canadian Union of Public Employees spokesman Hugh Pouliot confirmed the strike has started after no deal was reached.

Air Canada has said all flights will be canceled for the duration of the work stoppage. Canada’s largest airline has already canceled more than 620 flights, leaving travelers around the world stranded and scrambling during the peak summer travel season.

A bitter contract fight between Canada’s largest airline and the union representing 10,000 of its flight attendants escalated Friday as the union turned down the airline’s request to enter into government-directed arbitration, which would eliminate its right to strike and allow a third-party mediator to decide the terms of a new contract.