OTTAWA - - The federal labour minister says she's concerned about the possibility of a strike by Air Canada's largest union that threatens to disrupt the March Break travel plans of thousands of Canadians.

Lisa Raitt, who has moved swiftly in the past to intervene in labour disputes at the country's biggest airline, said Wednesday that a strike could also have a big negative impact on the economy.

"This is a particularly bad time for thousands of families," Raitt said in an emailed statement.

"We encourage both parties to avoid a work stoppage and restore confidence for the travelling public and Canadian job creators that rely on commercial air services."

The International Association of Machinists and Aerospace Workers -- representing about 8,600 mechanics, baggage handlers and cargo agents at Air Canada (TSX:AC.B) -- served notice late Tuesday that it intends to begin a strike at 12:01 a.m. ET on March 12 unless there's a new contract.

In a brief statement posted on the IAMAW Local 2323 website, the union says, "We are the largest unionized workforce at Air Canada, without us, it's all grounded."

However, Duncan Dee, Air Canada executive vice-president and chief operating officer, attempted to downplay the possibility of travel chaos should there be a strike.

"Should a settlement not be reached and the IAMAW commences job action, the airline will endeavour to minimize inconvenience to its customers," Dee said in a statement.

"The lines of communication remain open and we are hopeful that there remains sufficient time to avoid a work disruption."

Interim NDP leader Nycole Turmel urged the government not to step in to end the conflict before it has reached at least the mediation stage.

"We feel sorry the people who might be affected by the negotiation at Air Canada, but for us it is clear we need to let go the process to make sure that everything has been done to resolve the problems," Turmel said.

The Conservative government's recent history of intervening in Air Canada labour disputes, however, suggests it's not likely Ottawa will stand idly by.

Last month, Raitt -- insisting a work stoppage would not be in the best interests of the fragile Canadian economy -- stepped in to impose a six-month mediation process after the airline's pilots voted overwhelmingly in favour of a strike.

In September, the airline reached a deal with its flight attendants after a strike vote that prompted Raitt to warn of back-to-work legislation if a deal couldn't be reached. In June, a similar threat ended a walkout by the airline's customer service agents after just three days.

The latest sign of labour trouble came after Air Canada (TSX:AC.B) workers rejected a tentative contract settlement signed in February and gave their union a 78 per cent strike mandate.

Many Air Canada workers are trying to win back pay and concessions they gave up to help the airline restructure under bankruptcy protection in 2003 and 2004.

In its financial report issued last month, Air Canada said it lost $60 million in the fourth quarter of 2011 and $249 million for the year.

The airline is Canada's largest domestic and international full-service airline providing scheduled and charter air transportation for passengers and cargo to more than 175 destinations on five continents.

It is the world's 15th largest commercial airline, providing service to more than 32 million passengers a year.