The C-17 is the most flexible airlift aircraft to enter the Air Force's inventory. The ultimate measure of airlift effectiveness is the ability to rapidly project and sustain an effective combat force close to a potential battle area. Threats to U. S. interests have changed in recent years, and the size and weight of U.S. mechanized firepower and equipment have grown in response to improved capabilities of potential adversaries. This trend has significantly increased air mobility requirements, particularly in the area of heavy outsized cargo. As a result, additional airlift is needed to meet possible contingencies worldwide. The C-17 helps address these shortfalls in the current airlift force. The aircraft is operated by the Air Mobility Command with initial operations at Charleston AFB, S.C., with the 437th Airlift Wing and the 315th Airlift Wing (Air Force Reserve).