Hawker Hurricane
The Hawker Hurricane is a fighter design from the 1930's which was used extensively by the RAF during the Battle of Britain.
By most measures the design was outdated when introduced. It used a large measure of wood and fabric for the wings and fuselage, with the engine and cockput area being aluminum covered steel tubing. In contrast, the contemporary Supermarine Spitfire used monocoque construction and was thus both lighter and stronger.
But it was its simple construction that was the main reason it was ordered into production in 1936. It was unclear if the much more modern Spitfire would be able to smoothly enter production, whereas the Hurricane was a much more well understood system. This was true for service squadrons as well, who were well used to fixing wooden/metal planes like the Hurricane.
Although it may have been an older design, the Hurricane was still a worthy fighter on its own and a reasonable match for the Bf 109 it faced. Much of this was the result of the use of the very impressive Rolls Royce Merlin engine, which also powered the Spitfire. The Merlin was a much better engine in general terms than the Dailmer-Benz DB 601 used in the Bf 109.
By the close of the Battle of Britain in 1940, production of the Spitfire had ramped up to the point where all squadrons could be supplied with new machines. At this point the Hurricane was quickly relegated to 2nd line status. Nevertheless it would continue in production, largely in Canada, and was used in numerous roles like CAM and ground attack.