Paris - Air France on Wednesday estimated the cost of two-week pilots' strike last month at up to €500m ($633m).
Thousands of Air France flights were grounded by the September 15-28 strike over the company's plans to develop its low-cost subsidiary Transavia.
Air France-KLM traffic figures for September released Wednesday showed passenger numbers falling 16.3% to 5.7 million.
The Franco-Dutch group estimated the impact of the strike on third-quarter operating results, which will be published at the end of October, at €320-350m.
Adding the effect of the strike on bookings in the fourth quarter, the airline estimated the total impact of the longest-ever strike by Air France pilots at "around €500m."
The pilots' unions, who had drawn fierce criticism for their perceived intransigence from customers, ground staff and the government, ended the strike on September 28 despite failing to agree on a new pay deal for Transavia pilots.
Air France says it needs to reduce crew costs to make Transavia into a competitor to the likes of Ryanair and Easyjet.
- Sapa-DPA