Summary: GAO discussed its review of C-17 aircraft software development problems. GAO noted that: (1) the Air Force underestimated software complexity, and did not require the contractor to follow many basic software planning steps, institute good quality assurance practices, or separately track and report the status of software development; (2) when the C-17 test aircraft flew in September 1991, it was equipped with only two-thirds of the newly developed software needed to meet all of its operational requirements; (3) due to problems in developing and testing the software, the Air Force allowed the contractor to delay completion and installation of many mission-critical software functions; (4) the contractor diverted many of its resources away from software development and testing of the production aircraft to complete the first test flight, causing delays, and the required software will not be available until late 1992; (5) even with an adjusted schedule, the Air Force allowed the contractor to take other shortcuts which increased the risk of software development and testing; (6) the Air Force made computer system development decisions that could increase long-term hardware and software maintenance costs; (7) the Air Force established a complex and potentially expensive software maintenance environment by developing C-17 software in a diverse assortment of languages; and (8) the embedded C-17 computers need sufficient spare processing and memory capacity to service future growth.