Pursuant to a congressional request, GAO reviewed the Air Force's Cheyenne Mountain Upgrade (CMU) program, focusing on the: (1) current cost and schedule for the CMU program; (2) status of CMU subsystems development and performance; (3) status of the integration of CMU systems; and (4) management issues affecting future CMU development.

GAO found that: (1) the CMU program continues to experience cost increases and schedule delays; (2) major CMU subsystems are unreliable and do not meet users' requirements; (3) the Air Force has prematurely declared some subsystems operational; (4) because the Air Force is paying for some CMU subsystem development with funds designated for operations and maintenance, the cost of developing CMU is being understated; (5) significant incompatibilities among CMU component subsystems have been identified that could prevent the overall system from becoming fully functional; and (6) the Air Force has made improvements in program management and is considering further program management changes.