In 1996, the U.S. Department of Defense awarded Boeing a four-year contract for the concept demonstration phase of the Joint Strike Fighter, or JSF, program competition. The goal was to develop a low-cost, multirole tactical aircraft for the U.S. Air Force, Navy and Marine Corps, and the UK's Royal Navy and Royal Air Force. Boeing built two concept demonstration aircraft that validated the company's approach to commonality; low-speed handling qualities and carrier approach; and short-takeoff-and vertical-landing, or STOVL, hover and transition between conventional and vertical flight. Although not selected for full-scale development of the JSF, the program yielded many advances in stealth technology and design and manufacturing methods. These achievements have been applied to other Boeing programs including the F/A-18E/F Super Hornet and the X-45A Unmanned Combat Air Vehicle, or UCAV.