Around 1,000 flights to and from France were canceled Friday as the country's air traffic controllers went on strike, causing delays across European airspace.
France's DGAC civil aviation authority said 16 airports were operating a skeleton service, as were traffic control centers guiding planes overflying French territory at high altitude.
But several regional airports were closed and the DGAC warned of "cancellations and significant delays across the country.”
European air traffic body Eurocontrol said it was seeing "significant disruption," with delays totaling over 500,000 minutes by 8:30 a.m.
That was more than three times the level across the whole of last Friday when air traffic was moving normally.
Around 21,000 planes are expected to pass through Eurocontrol airspace Friday, down by around one-third.
Air France dropped around half its 800 planned services Friday, while Europe's largest airline, Ryanair, said it had canceled 420 flights.
The DGAC said it was working with Eurocontrol to divert planes around French airspace.
The SNCTA air traffic controllers' union said its members are concerned that pay is not keeping up with soaring inflation.
It also warns that recruitment is falling short, risking gaps in the profession's ranks when large numbers of existing workers retire from the end of this decade.
The union said it had filed notice of a further strike on Sept. 28-30.