PARIS -- A strike by air traffic controllers provoked flight cancellations and delays Monday at Paris' two main airports.

Traffic was most disrupted at Orly airport south of Paris, where France's civil aviation authority (DGAC) said earlier only one flight in two would be assured this week.

The cancellation of number of departures and arrivals for Monday morning has been announced at the airport's two terminals, as well as delays for several flights.

At Paris? bigger airport Charles de Gaulle only a number of delays were reported.

Called by the General Labor Confederation (CGT) union, the strike is over plans to centralize air-traffic control for the Paris region at a single base.