The dispute has already resulted in 15 days of walkouts this year, costing Europe's second-largest carrier by revenue up to 400 million euros (£351 million).

As the company hunts for a new CEO to replace outgoing Jean-Marc Janaillac, interim non-executive chairwoman Anne-Marie Couderc had sought to placate the unions earlier on Friday.

In a letter seen by Reuters, Couderc told the unions that Air France management would next week offer new measures aimed at ending the conflict.

The French government, already locked in a battle over reforms at state railway operator SNCF, has said it will not bail out Air France.

Last month an adviser to French President Emmanuel Macron said the government had no plans to reduce its 14.3 percent stake in Air France-KLM but might not maintain this level forever.

In a brief statement Air France-KLM said the strike was not compatible with concern for the future of Air France and confirmed that Couderc would meet union representatives on June 14 and come up with proposals.

(Reporting by Cyril Altmeyer; Writing by Matthias Blamont; Editing by David Goodman)