Summary: To modernize the National Airspace System, the Federal Aviation Administration (FAA) plans to switch from ground- to satellite-based navigation by using satellite signals generated by the Defense Department's Global Positioning System (GPS). However, GPS by itself does not satisfy all civil air navigation requirements, such as the one requiring that aircraft operators be provided timely warnings of system malfunctions and another requiring that the system be available virtually around the clock. As a result, FAA is developing a network of ground stations and geostationary communications satellites, known as the Wide Area Augmentation System (WAAS), to enhance GPS so that satellite-based navigation can meet those requirements. The Secretary of Transportation reported in February 1998 on the program's status and management. GAO examines whether the Secretary's report provides a complete assessment of FAA's risks in developing the WAAS project. GAO also examines how alternative assumptions would affect WAAS' benefit-cost analysis of January 1998.
