Aveos Fleet Performance Inc., a private company that maintains many of Air Canada's aircraft, shut down its plants on Sunday, locking out at least 2,400 workers and telling them not to return to work. Approximately 1,800 of the affected employees are based in Montreal, while 350 are in Winnipeg and 250 are in Vancouver, according to the International Association of Machinists and Aerospace Workers. "The maintenance component that supplies work to the Air Canada fleet has effectively ceased operations," Lorne Hammerberg, the IAMAW's local president in Winnipeg, told CBC News. "The base manager and his senior managers came down today to the hangars, told the guys they were no longer in operation and to remove themselves from the premises." Aveos posted a sign at its Winnipeg plant late Sunday afternoon, stating, "We regret to advise you that effective immediately, Aveos Fleet Performance Inc. has ceased the operation of airframe maintenance." Union officials in Vancouver confirmed that employees at the Aveos plant there had been told to go home and leave all their equipment and personal items behind. Aveos officials did not return calls by CBC News for comment on Sunday.