Two of the airline's cabin crew unions called the strike, which started on Wednesday after talks on renewing a collective labour agreement broke down.

Parent group Air France-KLM earlier on Wednesday said a strike by pilots in June had cost it around 40 million euros and CFO Pierre-Francois Riolacci said the cabin crew strike could cost more than that, or "several dozens of million euros".

Air France has said it will cancel around 13 percent of the flights planned for Wednesday as a result of the strike.

For Thursday, the airline will cancel around 30 percent of short and medium-haul flights from Paris Charles de Gaulle, while keeping around 90 percent of long-haul flights running. Around 80 percent of domestic flights will operate, it said.

The airline is, for example, trying to keep flights running between Paris and Amsterdam in order to transfer passengers onto the KLM network, which is not affected by the strike.

(Reporting by Victoria Bryan and Cyril Altmeyer; Editing by Geert De Clercq)