GAO discussed strategic mobility issues, focusing on the Department of Defense's (DOD) stated mobility requirements and mobility capabilities issues that have not been resolved. GAO noted that: (1) DOD has defined extensive strategic mobility requirements that are sensitive to the assumptions DOD used in studying the issue; (2) key assumptions about sealift capabilities were overly pessimistic, and key assumptions about airlift capabilities were overly optimistic; (3) the Army has increased the amount of equipment and supplies it has prepositioned in forward areas, and the Marine Corps has upgraded the firepower of its prepositioned equipment; (4) the Navy and the Maritime Administration (MARAD) are acquiring more roll-on/roll-off sealift ships, and the Navy is acquiring more container ships; (5) under existing airlift acquisition plans, DOD will not have the airlift capability it needs until 2005, primarily because of problems in the C-17 aircraft program; (6) DOD is taking steps to extend the service lives of the C-5 and C-141 aircraft by increasing the use of companion training aircraft, commercial aircraft, and flight simulators; (7) certain air bases in Europe are critical to meeting strategic mobility requirements, but they face a threat of closure during the ongoing military drawdown; (8) the Army has not completed improvements in its rail transportation capabilities; and (9) MARAD is acting to increase the readiness of ships in the Ready Reserve Force.