Extended Essay Throughout the 20th century, the Allied Air Forces during World War II experienced rapid advances in technology, primarily with the enormous amount of new aircraft that were being built , as well as the new tactics used. This advancement would greatly influence the present day as it pushed for the evolution of the Air Force, as it pushed the boundaries of what was possible. The Allied air forces consisted of the United States Army Air Forces, the Royal Air Force, and the Soviet Air Force, all of which increased in control and power as the war progressed, resulting in great improvements in aviation. became one of the most important aspects of the war soon after Hitler launched his invasion of Poland in September 1939. Prior to this, the United States Air Force consisted of only 20,000 personnel and fewer than 2,000 aircraft, later the Department of War was waged by the Army Air Forces. It grew significantly after Pearl Harbor, when the United States was pushed into war. With the help of General Henry Arnold's military leadership, the Air Force created one of the largest air fleets and took control of the aviation industry by promoting innovations in the planes that were produced. At the height of the war, the AAF was able to increase its personnel to 2.4 million and included over 80,000 aircraft. The Royal Air Force faced a similar fate to that of the United States in that after World War I, it had demobilized, resulting in a semi-weak air force. At the outbreak of the Second World War, the Royal Aircraft had only 2,000 aircraft, but by the end of the war there were 963,000 personnel involved. The Royal Air Force would… middle of paper… f 173 models of fighter aircraft were made during the war. Fighter aircraft best displayed the constant struggle for technological supremacy of the Axis and Allied powers, as each side seemed to be in desperate need of surpassing the other by improving the characteristics and capabilities of the aircraft. Credentials for the best fighter aircraft included top speed, the amount of armament they could carry, range, endurance, visibility from cockpit windows and overall flight performance. Two American fighters that received top honors were the North American P-51D Mustang and the Republic P-47D. For many the North American P-51D Mustang is considered the greatest fighter of World War II due to its range of 1140 miles which could increase to 2200 miles when external tanks were used. Its cockpit visibility received high marks, as did its speed and maneuverability.