Those workers belong to the Canadian Union of Public Employees, which says it plans to picket the airport in protest.
The changes are to take effect June 1.
CUPE Alberta president Marle Roberts said she hasn't been able to get a straight answer about whether the positions will be filled by temporary foreign workers.
"This is a red flag," she said. "It's the silence that is making us concerned."
The union is also concerned that with the privatization, the wages won't be high enough for the workers to make ends meet in the oilsands-centred city in northeastern Alberta.
The contract to clean the new airport terminal, which opened last June, was awarded to a local company called Bill's General Cleaning Services. Bill's had been servicing the city's old airport terminal, which now mainly handles workforce charters, cargo and private aircraft.
Bill Asefa runs the cleaning company, which has 40 employees and offices in Edmonton and Fort McMurray. He said he employs both Canadians and temporary foreign workers, but that he doesn't intend to recruit outside Canada for the new airport contract.
"Especially now, there are so many Canadians out of jobs," he said. "So that is the path I'm going to be looking at."
Scott Clements, president and CEO of the Fort McMurray Airport Authority, says the downturn in oil prices has meant a 25 per cent decrease in workforce charter flights.
Contracting out the cleaning staff was always part of the plan, but the economic environment has made cost-cutting all the more important.
"Our wage rates are way, way over market. Anything that's over market is vulnerable, let's face it," said Clements.
"We're under such pressure with US$50 oil, I just simply have to keep operating the business as an efficient one."
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