Pursuant to a congressional request, GAO reviewed the Federal Aviation Administration's (FAA) acquisition planning to date, focusing on the extent to which: (1) the schedule estimate for the Standard Terminal Automation Replacement System (STARS) is attainable; and (2) cost estimates to make STARS operational are likely to change. GAO noted that: (1) the STARS schedule, which calls for implementation of 171 air traffic control facilities between December 1998 and February 2005, is attainable only if FAA is successful in its efforts to mitigate certain risks; (2) specifically, FAA will need to obtain commitment by key stakeholders to the STARS schedule, resolve schedule conflicts between STARS and other modernization efforts, and overcome difficulties in developing system software that could delay implementing STARS; (3) FAA is aware that these issues pose a risk for STARS and has begun several risk mitigation initiatives; (4) while such actions are encouraging, it is too early to tell how effective they will be; (5) FAA's cost estimate for STARS has the potential to increase; (6) FAA's total cost estimate for STARS is $2.23 billion; (7) FAA approved this estimate in January 1996, however, a September 1996 analysis by agency officials pointed to potential cost increases that could drive the total cost estimate to as much as $2.76 billion; (8) this possible increase is attributable to expected higher costs for operating and maintaining STARS equipment; (9) FAA officials are continuing to revise the STARS cost estimate and now believe that cost increases may be significantly lower; and (10) at this time, however, FAA could not provide GAO with an updated estimate.