The Airbus A300 is a wide-body medium-to-long range airliner; it has the distinction of being the first twin-engine wide-body aircraft in the world. In 1977, the A300 became the first Extended Range Twin Operations (ETOPS)-compliant aircraft, due to its high performance and safety standards. Another world-first of the A300 is the use of composite materials on a commercial aircraft, which was used on both secondary and later primary airframe structures, decreasing overall weight and improving cost-effectiveness. Other firsts included the pioneering use of center-of-gravity control, achieved by transferring fuel between various locations across the aircraft, and electrically signaled secondary flight controls.