PARIS (AP) _ A pilots strike at Air France forced the troubled state-owned airline to cancel up to half of its domestic and European flights Wednesday, though most overseas flights went as planned, an airline spokesman said.

Those figures were disputed by unions, however, who said only half of the airline's overseas flights, and one-in-three of the shorter flights were operational.

Some pilots had returned to work, allowing the airline to keep many flights going Wednesday, spokesman Marie Clotilde Debieuvre said.

The airline said its flight program would be scheduled as normal for Thursday, though there was some risk of disruptions.

Unions disagreed, predicting even more canceled flights.

``From Thursday, the conflict will spread to include all of the long-haul flights,'' five pilots' unions said in a news release.

Pilot unions called a four-day strike to run through Friday to protest Air France's planned double-tier salary system for new pilots.

One of six unions pulled out of the strike Tuesday, after reaching agreement on the hiring of new pilots.

Air France Chairman Christian Blanc has said the strike could cost the company up to $17.8 million a day.