BRUSSELS, April 26 - Investigators for the European Parliament said Wednesday that data gathered from air safety regulators and others found that the Central Intelligence Agency had flown 1,000 undeclared flights over European territory since 2001.

Sometimes the planes stopped to pick up terrorism suspects who had been kidnapped to take them to countries that use torture, the investigators added.

The operation used the same American agents and the same planes over and over, they said, though they could not say how many flights involved the transport of suspects.

The investigation, by a committee looking into C.I.A. counterterrorism activities in Europe, also concluded that European countries, including Italy, Sweden and Bosnia and Herzegovina, were aware of the abductions or transfers and therefore might have been complicit.