The union representing Air Canada’s 10,000 flight attendants has served its 72-hour strike notice for their members to walk off the job as of August 16, amid contract negotiations with the airline.

The union representing around 10,000 Air Canada flight attendants issued a 72-hour strike notice Wednesday. In response, the airline issued a lockout notice.

The airline says gradual cancellations starting Thursday will lead to a full shutdown of Air Canada and Air Canada Rouge flights by the weekend