The Supermarine Spitfire was a British fighter of the WWII era. It was a single-engine, all-metal, low-wing monoplane with retractable landing gear. While the Mk VI variant was being designed, an earlier Mk VC was equipped with a new more powerful engine. It was hoped that this would quickly improve the plane's performance and result in an interim variant. The first two prototypes were powered by the Merlin 61 engine and took to the air early in 1942. Modifications to the prototypes improved the service ceiling by almost 10,000 feet, and the top speed by nearly 70 mph.
A total of 5,656 Mk IX were produced and 262 more Mk Vs were converted to Mk IX. Intended as a transitional stop-gap measure for the Mk VII and Mk VIII, the variant remained in production until the end of the war, ultimately becoming the most mass-produced Spitfire version. This mark was also used as a fighter-bomber and a reconnaissance plane.