This volume is a compendium of papers presented during an Advanced Seminar on Air Traffic Control (ATC) that took place in Capri, Italy on October 28-31, 1991. The Seminar was' organized by the Progetto Finalizzato Trasporti of the Italian National Research Council. The papers presented in the Seminar dealt with a wide range of topics which are currently important in ATC. For example, there were papers on such subjects as recent developments in primary and secondary radar technologies, communications networks and protocols, and the future uses of satellite-based communications, navigation and surveillance in ATC. However, all the papers contained in the volume were selected exclusively from that set of papers that addressed some aspect of the main area of emphasis in the Seminar, namely massive data-processing requirements and computer­ intensive problems in ATC. Data-processing requirements in A TC have grown enormously over the years. Obviously, the rapid increase in air traffic volumes in most of the world is one of the factors that has contributed to this growth. However, two other developments have contributed much more significantly: first, the ATC system now collects (mostly automatically) immensely more "information per flight" than in the past; and, second, as the system's complexity increases and as it becomes more tightly interconnected geographically, so grows the need to communicate, process and "filter" the data presented to the system's various components.