I remember hearing that the Japanese stole the design for the Zero from Howard Hughes and a plane he made. Is there any truth to this?
Hughes claimed that the Zero was based on his H-1 Racer. The standard statement accredited to him is this:
This quote can be found in many sources, though I can't seem to pin down where it originated from.
However, there is no evidence for that claim whatsoever. The Zero does share some superficial similarities to the H-1, mainly regarding the shape of its wing and tail structures and its use of a radial engine. However, the Mitsubishi A6M Zero was a follow-up to the Mitsubishi A5M, and both were designed by the same man, Horikoshi Jirō. Given that the A5M's first flight occurred before that of the H-1, I find it easier to believe that Jirō's A6M design was a natural evolution of the A5M rather than some copy of the H-1.
The Smithsonian write-up for the H-1 states:
This seems a bit more likely than the idea that the Zero was copied from the H-1. Nonetheless, I think that even this gives a bit too much credit to the H-1. As I mentioned before, the A6M was a follow-up to the A5M, which had a radial engine. The H-1 was definitely a faster aircraft than the A5M, so I suppose the H-1 did prove how fast a radial-engined aircraft could be, but the A6M would have almost certainly had a radial engine regardless of whether the H-1 was ever made. Radial engines have certain qualities that make them very appealing for carrier-based fighters, which is why all Japanese and American carrier fighters had them.
Basically, I think that the A6M Zero is far more clearly an evolution of the A5M than it is a copy of the H-1. The idea that the Japanese had to copy a foreign aircraft to make an effective fighter seems suspect to me, as the A5M was by far the best carrier-based fighter aircraft when it was introduced in 1935. The Japanese produced enough high-quality designs even during the war - aircraft such as the Kawanishi N1K, Kawasaki Ki-100, and Nakajima Ki-84 were all very effective fighters, capable of dealing with their American rivals, though not produced in sufficient quantities - which leads me to believe that Japanese aircraft designers were quite capable of coming up with good creations on their own.
There really is not much substance to this claim as the Zero and the Hughes H-1 represented different design philosophies. The Hughes racer emphasized speed and engine power, whereas Horikoshi's A6M prioritized maneuverability and long range. The Hughes design was notable for using a radial engine and flush riveting, two design features that the Zero utilized, but this was much less copying by the Japanese and more reflective of a generalized developments in aviation technology of which Mitsubishi was a participant.
A better claim for influencing the Japanese was the Vought V-141 of which the Japanese had acquired a copy in 1937. However, a lot of the resemblances are superficial and again represent more of a general trend in aviation technology than plagiarism.
The notion that Japan copied or stole its successful designs stemmed from wartime notions that Japan was simply incapable of producing something that matched Western designs. This denigration is not just limited to aviation designs. For example, Hector Bywater's 1925 war novel The Great Pacific War featured a Japanese aerial attack on Pearl Harbor. This has entered into popular discourse, especially among Pearl Harbor conspiracy partisans, that the genesis of Pearl Harbor came from this novel. Much of this is tinged with racism as it makes the implicit assumption that Japan was not capable of being as innovative as the West.
Sources
Mikesh, Robert C. Zero. Osceola, WI: Motorbooks International, 1994.
Peattie, Mark R. Sunburst: The Rise of the Japanese Naval Air Power, 1909-1941. Annapolis, Md: Naval Institute Press, 2001.