Parent Air France-KLM aims to reduce costs by at least 1.5 percent this year with initiatives such as a new Air France unit, dubbed Boost, that would operate at lower costs out of its hub at Charles de Gaulle in Paris.

In a referendum of all Air France pilots, some 58.1 percent supported the idea in principle after a turnout of 73.8 percent, the union said in a statement, adding that it took note of the decision.

Pilots were voting on the principle rather than the plan itself. The 'yes' vote overcomes one key hurdle for the airline's management, but the plan is subject to detailed talks with pilots and cabin staff before it can go ahead.

Pilot costs would be cut by 15 percent and cabin crew by 40 percent under the proposals, which were greeted with scepticism by pilots' unions when presented by Air France last week.

(Reporting by Tim Hepher, Cyril Altmeyer)