During the Korean War, planes had to go through a redesign to compete during the war. Planes became supersonic, and a multirole purpose for them was needed. As well, guns on planes proved ineffective at high speed. The results were Second Generation Aircraft such as the American Century series (planes from F-100 to F-106), the Soviet MiG-21, the most widely produced plane in the 20th century, the British Electric Lightning, and the French Dassault Mirage III.