Hundreds of flights in France were cancelled Tuesday as air traffic controllers went on strike against tweaks to a long-running EU project aimed at creating a single European airspace.
The modified project aims to open parts of the sector up to competition and cut costs, prompting criticism from France, Germany and unions that fear it will see people lose their jobs and jeopardise safety.
Controllers in 10 other European countries are also due to stage protests Wednesday against the project.
"The problem doesn't lie in the 'single sky' regulations that aim to harmonise air traffic management at a European level, we're for that," said Olivier Joffrin of the USAC-CGT, one of the unions involved.
"What we don't accept is that the Commission use this to privatise and liberalise some activities," he said, pointing to radar maintenance as an example of services that may be opened up for competition.
Joffrin said that outsourcing these services could present a security risk and could also threaten current jobs.
Paris and Berlin have asked the European Commission to postpone the modified project, French transport minister Frederic Cuvillier said Tuesday, as 1,800 flights were cancelled -- just under a quarter of the daily average.
"France does not support this new initiative from the European Commission," Cuvillier said.
The French strike was initially expected to last until Thursday evening, but will now only be held for two days in light of Cuvillier's statement of support, the controllers' main union said.
Irish low-cost carrier Ryanair blasted the work stoppage, saying passengers were being "taken hostage" and calling on the European Commission to put an end to controllers' strikes after it had to cancel more than 100 flights.
Air France, meanwhile, said it expected all long-haul flights from Paris would go ahead, but did not exclude "last-minute delays and cancellations".
The controllers' action is just one of the planned strikes in France this week, with railway workers due to stop work from Wednesday evening until Friday morning, and postal service employees expected to strike Thursday.
The "Single European Sky" aims to bring management of European airspace under EU control.
Fragmented country-by-country air control is currently estimated to bring extra costs of close to five billion euros ($6.6 billion) a year to airlines and passengers in Europe, and adds to the distance of an average flight.
The European Commission wants to redesign the EU's 27 national airspaces into just nine bigger sectors, saying a "single" European sky would improve safety tenfold, slash pollution by 10 percent and reduce costs by 50 percent.