Paris, France (CNN) -- A strike by air-traffic controllers affected flights Wednesday across France, resulting in cancellations of 10 percent of scheduled flights from Paris' main international airport, the civil aviation authority DGAC said.
In addition to the cancellations at Roissy Charles de Gaulle Airport, half of the flights from Orly, the nation's second-largest airport, were canceled, the authority said.
Would-be passengers were urged to contact their airlines prior to traveling to the airport.
Ireland's low-cost airline Ryanair called Wednesday for the French government to get the French military, "if necessary," to take over air traffic control duties while civilian air traffic controllers are on strike. "France, passengers and airlines cannot afford these airport closures at a time when traffic and tourism is suffering," Ryanair said in a statement.
The timing coincides with the beginning of summer vacations for many French. One EasyJet passenger who was at Orly when she found out her flight had been canceled until Thursday bemoaned her situation. "In the middle of July, it's tough to find a place to stay," said Nawel Boubouka.
The strike started Tuesday evening and is scheduled to end Thursday at 6 a.m.
Controllers are striking over plans to unify European air traffic control.
France is due to join Germany, Switzerland, Belgium, the Netherlands and Luxembourg to form what is being called Functional Airspace Block Europe Central (FABEC).
FABEC is a cornerstone of the Single European Sky project, which advocates say will reduce fuel use and flight times by making it possible for planes to fly more direct routes across the continent.
The FABEC area covers 1,713,442 square km (661,560 sq miles) and is characterized by closely interlaced civil and military traffic routes, its website says.
Most of the large European airports and major civil and military airways are located in the FABEC area.