After World War I, Russia began building its most prolific aircraft, the MiG line. MiG pilots fought with distinction in WWII, but the MiG heyday hit with the design of the MiG-15, a copy of a Nazi experimental jet. During the Korean War, MiG-15s dueled with U.S.A.F. F-86s over Korea. Later, the MiG-21 contested the skies over North Vietnam as they duked it out with American Air Force and Navy jets.