Area Navigation Systems (RNAV), coupled with appropriate air traffic control techniques, promise to improve the movement of aircraft within the National Airspace System (NAS). These systems are based upon use of the NAS ground radio navigation aids by the airborne navigation receivers, and other sensors available in today's aircraft.The evolution and product development of airborne equipment for this purpose have been guided by airline and FAA operational needs. The airline industry, through its Air Transport Association (ATA) and Airline Electronic Engineering Committees (AEEC), is standardizing the requirements for three classes of equipment. These are: Mark I RNAV, simple, yet requiring considerable pilot manual operation; Mark II RNAV, virtually automatic, with new cathode-ray tube multi-function/navigation displays for the pilot; and Mark III (Mark 13) RNAV, based upon use of the self-contained inertial navigation systems presently installed in today's large jets.Airline experimental programs have provided insight into the need for certain pilot workload reduction features and capabilities. The airframe and avionic equipment manufacturers are following these guidelines in the development and application of these systems in the next generation wide-body jets, soon to enter airline service. This paper presents descriptions of the different classes of RNAV equipment, along with operational advantages of the pilot displays.