The development of United Air Lines operational computer system is described. This is a medium-volume general-purpose on-line system with off-line capability, the need for such a system arose from the decentralized nature of airline operations coupled with the increasing need to automate many areas of company operations in addition to the traditional reservations and accounting functions. The computer utility is designed to handle all of the airline's message switching, flight planning and monitoring, and aircraft parts inventory control. Also under evaluation and implementation are applications involving airport terminals and air freight control.