Air France pilots are threatening to strike for several hours a day throughout May to protest against what they say are limits on their right to strike.
The carrier warned that the action would disrupt its schedule and prevent flight connections at the Paris Charles de Gaulle airport.
The airline plans to cancel most of the flights threatened by the walk out.
Leading pilot union SNPL said it plans daily strikes between 5.45am and 7.45am and 12.45pm and 3.45pm between May 3 and May 30.
The union wants the cancellation of a law that forces them to give 48 hours’ notice for a strike.
An airline spokesman said: “This strike action is unusual both for its significance, lasting nearly a month, as well as for its methods which will penalise Air France flights at two peak times of day.”
Air France-KLM chief executive Alexandre de Juniac said the strike could cut revenues by up to several tens of millions of euros per day, Reuters reported.
“It is an act of disrespect towards passengers and staff,” he said.
The French transport ministry said the mandatory notice does not infringe on the right to strike but allows companies to warn passengers of possible delays to their flight.