Air France has estimated that last month's strike will cost it about €500mln in lost revenue, BBC News reports.

The struggling French flag carrier was in dispute with pilots over plans to expand its budget subsidiary Transavia.

Finance director Pierre-Francois Riolacci said there would be an immediate impact of about €320-350mln, plus loss of future business.

Shares in Europe's second-biggest airline fell 2%, at one point touching the lowest level in a year. The company has already cut its profit target for 2014.

Air France said that total passenger traffic fell 15.9% in September, adding that bookings for the next three months were also down.

The airline put the expansion of its Transavia budget carrier on hold after the two sides agreed to talks. Pilots objected that the move of staff to Transavia would erode existing contracts.

Air France wanted to expand its budget division to compete with the likes of Ryanair and easyjet.

Prime Minister Manuel Valls warned last month that the two-week strike was creating "real danger" for the airline and the image of France.