Air Canada is considering ceasing flights out of Billy Bishop Airport in downtown Toronto amid a continuing push to cut overall costs and failed efforts to gain more access to the airport.

"While Air Canada's traffic and load factor at Billy Bishop Toronto City Airport increased in 2014 over the previous year, as part of its continuing cost transformation initiatives, Air Canada is assessing the viability of Billy Bishop operations based on current imposed terminal rates and terms," the airline said in a statement.

The airport is owned and operated by the Toronto Port Authority, but its biggest user by far is Porter Airlines Inc., which owns the terminal at the airport but has put the building up for sale.

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Porter's domination of the airport and the limits placed on take-off and landing slots have led Air Canada chief executive officer Calin Rovinescu to criticize the airport as a "private playground."

Air Canada offers 15 flights a day out of Billy Bishop, which permits only turbo-prop planes to use the airport. That's less than 1 per cent of Air Canada's total daily 1,500 flights across Canada.

But a proposal by Porter to fly jets out of the airport and extend a runway into Lake Ontario to do so has led to a heated debate in Toronto about the future of the airport.

Porter has made a conditional purchase of Bombardier Inc. C Series jets, which are not carrying passengers yet, but are being flight tested.

The plane is more than two years behind schedule, though Bombardier has insisted it will be delivered to customers later this year.

Both Bombardier and Porter have said the C Series will meet current noise guidelines at Billy Bishop, but residents of the area near the island airport and along flight paths are concerned about increased traffic and congestion.

Air Canada spokesman Peter Fitzpatrick said he is unable to comment on the Billy Bishop issue beyond what the airline said in its statement, which was one paragraph in a news release outlining its December and year-end traffic.

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The airline's load factor was 82.6 per cent in December amid a capacity increase of 8.5 per cent.

The full-year load factor was a record 83.4 per cent up from 82.8 per cent in 2013.