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What was the most-built Spitfire variant?
Short answer
The Mk V: 6,487 examples were built, more than any other version, ahead of the 5,656 Mk IXs. Total production reached 20,351 units of all variants when the last Spitfire left the factory in February 1948. The Mk IX was born as a stopgap against the Focke-Wulf FW 190A.

The Mk V, the most-built version
The Mk V was produced in greater numbers than any other variant, with 6,487 units. More Spitfire Mk Vs were built than any other type, with 6,487 examples, followed by 5,656 Mk IXs.
The Mk IX, second in number
The Spitfire Mk IX was originally developed as a stopgap measure in response to the appearance of the Focke-Wulf FW 190A. Though conceived only as an interim type, the new aircraft, designated Type 361, would end up as the fighter's second most numerous variant. What was meant as a makeshift design became the backbone of Fighter Command. Initially 1,255 F.Mk IXs were produced, followed by 4,010 LF.Mk IXs and 410 HF.Mk IXs; with conversions and the similar Mk XVI variant, total production reached 7,011 aircraft.
A decade on the production line
Between 1938 and 1948, 20,351 Spitfires were built. When the last one rolled off the line in February 1948, 20,351 examples of all variants had been manufactured, including two-seat trainers. The Supermarine Spitfire was the only British fighter to remain in production before, during and after the Second World War.
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