At the beginning of World War II, U.S. aviation possessed aircraft of varying types and sophistication levels. While American fighters initially lacked significant advantages over enemy aircraft, designers soon created outstanding combat planes to overcome this deficit. In 1942, North American developed the P-51 Mustang, which became one of the world's finest piston fighters. British combat aviation also entered the war with diverse fighter types, with the Spitfire emerging as their standout aircraft. The Spitfire not only became Britain's most mass-produced fighter but remained in service in several countries until the 1960s. In U.S. front-line bomber aviation, the B-26 Marauder played a notable role, seeing widespread use in the European theater during 1944-1945. The exceptional combat experience and expertise of U.S. and British pilots, combined with their aircraft's superior technical capabilities, enabled them to turn the tide of the air war in Western Europe and achieve air supremacy.