: An operational Air Surveillance System shall generate a stable and reliable air picture. In dense target situations the quality of available sensor data is reduced. System models which take into account correlated flight paths of aircraft formations help to compensate the lack of information in dense situations. The paper presents algorithms to detect groups, to evaluate the relative behavior of group members and to handle group maneuvers and split and join events. The integration of group tracking into a complex operational system is additionally taken into account.