Customer service agents and call center workers walked off the job Tuesday at 12:01 a.m. and were replaced by 1,700 managers and non-union staff at Canada's nine largest airports.
The key issue is pensions for members of the Canadian Autoworkers Union.
Labor Minister Lisa Raitt told Parliament the government was giving both sides notice Tuesday afternoon they had 48 hours to reach an agreement or the government would enact back-to-work legislation.
"We are concerned by the effect that this strike will have on our economic recovery, which is still fragile, and on Canadians in general," Raitt said.
The minister told The Globe and Mail newspaper the legislation could begin with an order for both sides to go into arbitration.
"Nobody knows what the content of the legislation is, and right now both parties should be wondering whether or not they would do better making their own deal at the table," Raitt said.
CAW national president Ken Lewenza called the Conservative government's actions "shocking interference" on the first day of the strike.
"This action by the government is a clear interference with the right to free collective bargaining," Lewenza said.
The airline, which reported losses of $19 million in the first quarter of the year, has some 22,000 other employees who are not on strike.