Although Germany had entered the war in September 1939 as the world's leading air power, with 4,840 frontline aircraft and an aircraft industry producing 1,000 airplanes a month, the Luftwaffe's arsenal had serious defects. For one, Germany had never developed a satisfactory long-range bomber, in part because the German military's focus on blitzkrieg (lightning war) emphasized production of medium-range bombers and ground-attack aircraft, which had proven so successful in the Spanish Civil War. Germany's defeat in the Battle of Britain revealed the flaw of this policy from a strategic standpoint, as aircraft such as Heinkel He-111, Dornier Do-17, and Junkers Ju-87 proved ineffective against a technologically well-equipped enemy force. Likewise, Germany's lack of long-range bombers prevented it from conducting long-range air operations at sea or striking Soviet manufacturing centers relocated deep within the Soviet Union. Despite the damage inflicted by the Allied air campaign, the German armaments industry, ably led by Fritz Todt and Albert Speer, not only managed to increase production from 8,295 aircraft in 1939 to 39,807 in 1944 but also introduced the world's first jet fighter, the Messerschmitt Me-262, in the second half of 1944. These successes, however, proved to be too little and too late to make a difference, and the Allies had air supremacy in the last two years of the war.
As with Germany, Japan entered the war with a powerful air arm, which included some 2,900 combat-ready aircraft on 7 December 1941. Yet, Japan's attack on Pearl Harbor was in part a desperate gamble designed to cripple the United States to purchase time for Japan to build a defensive perimeter before U.S. industrial might reached heights that Japan knew it could never equal. Indeed, Japanese industry produced just 5,088 aircraft in 1941, compared with 26,277 for the United States. Failure to destroy the U.S. carriers in the surprise attack on Pearl Harbor ranks as a clear strategic mistake for Japan. Once it lost the Battle of Midway in early June 1942, Japan was forced into a defensive war in which it could not compete with the American war machine. Despite Allied attacks that crippled its shipping industry and weakened its industrial infrastructure, Japan still managed to produce 28,180 aircraft in 1944, a testament to the perseverance of its workers on the home front. That the United States produced 96,318 aircraft during the same year is a testament to the futility of Japan's challenge to American industrial might.
Although Benito Mussolini had built a powerful Italian air force in the late 1920s and early 1930s, by the beginning of World War II in September 1939, Italy's air force had become largely obsolete. This decline was in part a reflection of Italy's weak economy. When Italy joined the war on 10 June 1940, barely half of its 3,296 aircraft were of combat quality. While assistance from Germany (particularly in supplying aircraft engines) allowed the Italian aircraft industry to make modest increases from 2,142 aircraft produced in 1940 to 3,503 aircraft in 1941, Italy's weak industrial sector could not withstand the impact of the Allied bombing campaign, and production dropped to 2,818 aircraft in 1942 and just 967 aircraft by the time Italy surrendered in September 1943.
Although Germany enjoyed a great lead in the number of its combat-ready aircraft at the start of the war, Great Britain had an advantage in that its industry was in the process of introducing aircraft (such as the Hawker Hurricane and Supermarine Spitfire) more technologically advanced than their German counterparts. This qualitative advantage would prove critical to defeating Germany in the Battle of Britain. Secure from the threat of German invasion, British industry succeeded not only in increasing productive capacity with each passing year of the war but also in introducing aircraft such as the Handley Page Halifax and Avro Lancaster that played a critical role in the Allied bombing campaign against Germany. Great Britain's highest annual production total rea