WINNIPEG - Aveos Fleet Performance Inc., a company that provides aircraft maintenance to Air Canada, has shut down its plants in three cities, telling more than 2,400 workers they're being laid off and should not return to work, a union leader said Sunday.

Tony Didoshak with the International Association of Machinists and Aerospace Workers said Aveos employees were given the notice simultaneously at 1:30 p.m. ET on Sunday in Montreal, Winnipeg and Vancouver.

The union, which also represents Air Canada's mechanics, baggage handlers and ramp personnel, had feared for Aveo's future after Air Canada moved to subcontract some of its work offshore.

"It is my understanding that Aveos has ceased operations," said Didoshak, who is the union's general chairman in Winnipeg.

Didoshak said union officials haven't been able to reach anyone with Aveos to confirm the layoffs. Attempts by The Canadian Press to reach the company were also unsuccessful.

Air Canada (TSX:AC.B) has moved maintenance of landing gear and engines out of Aveos facilities and is sub-contracting work to other maintenance providers, including to China. The airline has also delayed some work until the fall.

Aveos was once Air Canada's technical services division but was later spun off as a separate company. The airline is Aveos' largest customer, providing about 90 per cent of its maintenance overhaul work.

Its exclusive contract expires in June 2013 and Air Canada has issued a request for proposals for future contracts.

Fred Hospes, chairman of the IAWAW District 140 Western Region, said earlier this month that the union was seeking conciliation — a process involving federal officials — in a bid to get more details about the financial difficulties facing Aveos.

Didoshak said work slowed down about three weeks ago in Winnipeg where Aveos services Air Canada's Embraer 190 jets.

"We had aircraft that were supposed to show up that haven't been showing up," Didoshak said.

No one from Air Canada could be reached on Sunday evening to respond to how the Aveos plants shutdown would affect the airline, which is in the middle of a bitter labour dispute with its pilots.

On Sunday, the airline asked the Canada Industrial Relations Board to step in after an unusually high number of pilots called in sick over the weekend, causing some flights to be cancelled or delayed.

_ By Rob Drinkwater in Edmonton.

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• Labour Day: A Canadian Invention

  Few Canadians realize it, but Labour Day is as Canadian as maple bacon. It all began in 1872, when the Toronto Typographical Union went on strike to demand a nine-hour workday. When <i>Globe and Mail</i> chief George Brown had the protest organizers arrested, Prime Minister John A. Macdonald passed a law legalizing labour unions. Thus, a Conservative prime minister became a hero to the working class, and Canada became among the first countries to limit the workday, doing so decades before the U.S. The typographers' marches became an annual event, eventually being adopted by the U.S., becoming the modern day Labour Day.

• The Winnipeg General Strike

  The end of World War I brought social instability and economic volatility to Canada. On May 15, 1919, numerous umbrella union groups went out on strike in Winnipeg, grinding the city to a halt. Protesters were attacked in the media with epithets such as "Bolshevik" and "Bohunk," but resistance from the media and government only strengthened the movement. In June, the mayor ordered the Mounties to ride into the protest, prompting violent clashes and the death of two protesters. After protest leaders were arrested, organizers called off the strike. But the federal mediator ended up ruling in favour of the protesters, establishing the Winnipeg General Strike as the most important strike in Canadian history, and a precursor to the country's modern labour movement.

• The Regina Riot

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• Bloody Sunday

  In May, 1938, unemployed men led by communist organizers occupied a post office and art gallery in downtown Vancouver, protesting over poor work conditions at government-run Depression-era "relief camps." In June, the RCMP moved in to clear out the occupiers, using tear gas inside the post office. The protesters inside smashed windows for air and armed themselves with whatever was available. Forty-two people, including five officers, were injured. When word spread of the evacuation, sympathizers marched through the city's East End, smashing store windows. Further protests against "police terror" would be held in the weeks to come.

• Giant Mine Bombing

  In 1992, workers at Royal Oak Mines' Giant Mine in the Northwest Territories went on strike. On September 18, a bomb exploded in a mineshaft deep underground, killing nine replacement workers. Mine worker Roger Warren was convicted of nine counts of second-degree murder. The Giant Mine closed in 2004.

• The Toronto G20

  The Canadian Labour Congress, representing numerous labour groups, participated in protests in Toronto during the G20 summit in June, 2010. When a handful of "Black Block" anarchists rioted through the city core, it brought an overwhelming police response that resulted in the largest mass arrests in Canadian history. More than 1,000 people were arrested, with most never charged with any crime. Numerous allegations of police brutality have been made, and the Toronto police are now the target of several multi-million dollar lawsuits. So far, two police officers have been charged with crimes relating to G20 policing, and charges against other police officers are also possible.

• Occupy Canada

  When Vancouver-based magazine Adbusters suggested the public "occupy Wall Street" to protest corporate malfeasance, New Yorkers took the suggestion seriously, and occupied Zuccotti Park in Manhattan. Canadians followed suit, sparking copycat occupations in all major Canadian cities in September, 2011. By December, most of the occupations had been cleared, all of them non-violently. Though the protests achieved no specific goals, they did change the political conversation in North America. What their long-term legacy will be remains to be seen.