Air France-KLM passengers face severe disruption throughout May if, as planned, pilots strike for several hours each day in a dispute over "limits" on their right to strike.
French pilots union SNPL is calling on its members to walk-out for set periods of each day from May 3 to 30.
The union is calling for strikes two hours in the morning and three hours in the afternoon.
Air France said the strikes could "seriously threaten its recovery", as most of the flights affected will have to be cancelled.
A spokesman for the airline 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."
SNPL is calling for industrial action because it is unhappy with a new law that forces pilots to give airlines 48-hours notice of any strike action, giving the companies time to draft in pilots from other airlines or to notify passengers of cancellations.
The union wants the law repealed so that future strikes will have their intended effect of causing maximum disruption.
In a letter to SNPL, Air France's chief executive Frederic Gagey said the strike "is taking place at a crucial time in Air France's recovery".
After six years of financial losses that led to radical cost-cutting measures including thousands of job cuts, the airline is aiming to generate a positive operating income this year a target it says could be damaged by the strike.
Gagey said: "It seems inconceivable that a strike, the grounds of which in no way concern Air France, can curb this momentum."