Air France KLM's low-cost unit Transavia said it was cancelling around 25% of its French flights on Thursday due to a strike protest among some staff over pay and working conditions.
Dozens of cabin attendants, stewardesses and stewards have been on strike since Wednesday, the national union of cabin crew SNPNC said, which plans to have its actions last until July 17.
Transavia's management had to cancel 15% of its flights on Wednesday.
The SNPNC want a complete review of salaries next January, adding the latest aid measures offered by the management to cope with soaring inflation were not enough.
Management said it planned to hold talks on the topic at the start of next year.