HUMAN ERROR IN ATC SYSTEM OPERATIONS

Air traffic control (ATC) system errors rarely occur in today's system. ATC-related aircraft accidents are even rarer events. Nevertheless, more than 90% of all the system errors that do occur stem from human mistakes in attention, judgment, and communications by controllers and their supervisors. Current levels of air traffic are already pressing the capacity of today's system. Resultant traffic congestion and controller work load, despite automation efforts, could increase the error rate and degrade the system's tolerance for errors. Several ATC-related aircraft accidents are summarized to illustrate the controller's changing role and the manner in whcih the controller interacts with pilots, other controllers, and the work environment. These cases also cite exemplary performance, as well as mistakes, by pilots and controllers, and the circumstances that fostered them, to illustrate the strengths and weaknesses of the human element in the present system. Implications for future ATC system design are discussed.