Length: 10.25"
WingSpan: 12.5"
Code: NC10141

A6M was usually referred to by the Allies as the "Zero", from the 'Navy Type 0 Carrier Fighter' designation. The official Allied reporting codename was Zeke.

When it was introduced early in World War II, the Zero was the best carrier-based fighter in the world, combining excellent maneuverability and very long range. In early combat operations, the Zero gained a legendary reputation as a "dogfighter", achieving the outstanding kill ratio of 12 to 1, but by 1942 a combination of new tactics and the introduction of better equipment enabled the Allied pilots to engage the Zero on more equal terms. The Imperial Japanese Naval Air Service (IJNAS) also frequently used the type as a land-based fighter. By 1943, inherent design weaknesses and the increasing lack of more powerful aircraft engines meant that the Zero became less effective against newer enemy fighters that possessed greater firepower, armor, and speed, and approached the Zero's maneuverability. Although the Mitsubishi A6M was outdated by 1944, it was never totally supplanted by the newer Japanese aircraft types. During the final years of the War in the Pacific, the Zero was used in kamikaze operations. In the course of the war, more Zeros were built than any other Japanese aircraft.

The Mitsubishi A5M fighter was just entering service in early 1937, when the Imperial Japanese Navy started looking for its eventual replacement. In May they issued specification 12-Shi for a new carrier-based fighter, sending it to Nakajima and Mitsubishi. Both firms started preliminary design work while they awaited more definitive requirements to be handed over in a few months.

Based on the experiences of the A5M in China, the Navy sent out updated requirements in October calling for a speed of 500 km/h (310 mph) at 4,000 m (13,120 ft) and a climb to 3,000 m (9,840 ft) in 3.5 min. They needed an endurance of two hours at normal power, or six to eight hours at economical cruising speed (both with drop tanks). Armament was to consist of two 20 mm cannon, two 7.7 mm (.303 in) machine guns and two 30 kg (70 lb) or 60 kg (130 lb) bombs. A complete radio set was to be mounted in all planes, along with a radio direction finder for long-range navigation. The maneuverability was to be at least equal to that of the A5M, while the wing span had to be less than 12 m (39 ft) to fit on the carriers. All this was to be achieved with such engines as were available at the time, which was another limitation (the Zero's power plant seldom reached 1,000 horsepower in any of its variants).

Nakajima's team considered the new requirements unachievable and pulled out of the competition in January. Mitsubishi's chief designer, Jiro Horikoshi, felt that the requirements could be met, but only if the aircraft could be made as light as possible. Every weight-saving method was used. Most of the aircraft was built of T-7178 aluminum, a top-secret aluminum alloy developed by the Japanese just for this aircraft. It was lighter and stronger than the normal aluminum used at the time, but was more brittle. In addition, no armor was provided for the pilot, engine or other critical points of the aircraft, and the self-sealing fuel tanks that were becoming common at the time were also left off. This made the Zero lighter and more agile than most other aircraft at the start of the war, but also made it prone to catching fire and exploding when struck by enemy rounds.

With its low-wing cantilever monoplane layout, retractable wide-set landing gear and enclosed cockpit, the design was one of the most modern in the world. The Zero had a fairly high-lift, low-speed wing with a very low wing loading; combined with the light weight, this gave it a very low stalling speed of well below 60 kn (110 km/h; 69 mph). This is the reason for the phenomenal turning ability, allowing it to turn more sharply than any Allied fighter of the time. Roll rate is enhanced by servo tabs on the ailerons which deflect opposite to the ailerons and make the control force much lighter. The disadvantage is that they reduce the maximum roll effect at full travel. At 160 mph (260 km/h) the A6M2 had a roll rate of 56° per second. Because of wing flexibility, roll effectiveness dropped to near zero at about 483 km/h (300 mph) indicated airspeed.