MONTREAL - The clock is ticking towards Air Canada's second strike this year and potentially the big carrier's most costly labour dispute in 13 years.

Negotiators for the airline and the union representing flight attendants are meeting this weekend trying to hammer out a new contract.

The Canadian Union of Public Employees gave strike notice on Friday night, meaning the flight attendants could walk out as early as Wednesday.

An earlier deal was rejected by the flight attendants and forced the company and union back to the bargaining table.

Hanging over the heads of the two sides is believed to be a government threat to quickly order an end to a strike.

Federal Labour Minister Lisa Raitt has invited both sides to a meeting if they can't hammer out a deal this weekend.