French air traffic controllers are striking over EU plans to merge civil aviation authorities in six countries amid fears it could lead to job losses.
The action will last until early Thursday.
Brussels wants to combine French air traffic authorities with those in Germany, Switzerland, the Netherlands, Luxembourg and Belgium.
The walkout has grounded flights across France.
The European Commission hopes the so-called Single European Sky will improve security, boost capacity and cut the cost of air-traffic services.
But unions say that will put jobs at risk.
Members fear the changes will mean surrendering their civil servant status and generous perks, including an estimated 30 weeks holiday a year.