The Spitfire IX was developed as a stopgap measure to counter the Luftwaffe's Focke-Wulf 190. The Spitfire VIII had been the RAF's initial response to this new threat, but the aircraft involved a significant overhaul of the basic Spitfire design, and would therefore take a considerable amount of time before the required numbers could be fielded.
Utilizing the same Merlin 60/70 engine as the Spitfire VIII, the Spitfire IX required only a slight modification to the Spitfire Vc fuselage to produce. This therefore allowed for faster production and development.
Taking to the skies for the first time on 26 February 1942, test flights were so successful that it was slated for immediate production. In July 1942, a Spitfire IX was tested against a captured Focke-Wulf 190A where it was discovered that the two aircraft had similar performance capabilities. The RAF had indeed found its answer to the Focke-Wulf 190.
The Spitfire IX was the most produced type of all the Spitfire variants. On 5 October 1944, the Spitfire IX had the unique distinction of being the first fighter to shoot down the German Me 262 jet-powered fighter.
