Air Canada’s flight attendants are one step closer to walking off the job after the Canadian Union of Public Employees (CUPE) served a 72-hour strike notice early Wednesday morning.

The notice means union members could begin strike action at 12:58 a.m. Eastern Time on Saturday.

Within an hour of the union’s move, Air Canada issued its own lockout notice. The airline has said negotiations have reached an impasse, while CUPE claims the company no longer wants to negotiate.

The dispute centres on a new collective bargaining agreement for flight attendants at both Air Canada and Air Canada Rouge.

On Monday, the airline proposed settling the matter through binding arbitration — a process that would have suspended both the union’s right to strike and the company’s right to lock out employees. The union rejected that offer, saying members had voted overwhelmingly in favour of job action if necessary, with a 99.7 per cent strike mandate approved last week.

Air Canada says in the event of a work stoppage, it will notify affected passengers and provide full refunds for cancelled flights through its website or mobile app.