French air traffic controllers went on strike Wednesday, prompting the cancellation of 40 percent of flights across France.

The powerful SNCTA union called the two-day strike in a quarrel over working and retirement conditions, saying in a statement that "disruption is expected over the whole country."

France's main airline, Air France, said long-haul flights would not be affected, and guaranteed some 60 percent of medium-haul flights from and to Paris' main airport, Charles de Gaulle.

Air France said it would ground two out of three flights at Paris' second-largest airport, Orly.

France's civil aviation agency said part of the dispute involves conditions for raising the retirement age for controllers from 67 to 69 years.

It advised passengers to contact their airline for more information.

Further strikes are planned April 16-18 and April 29-May 2, coinciding with spring school holidays in France.