Vickers Supermarine
Spitfire Mk XV

The XV and 17 marks were reserved for the naval version, the Seafire, in an effort to reconcile the Spitfire numbering scheme with that of the Seafire.

Mk. XVI

The Mk. XVI was identical to the Mk. IX in all respects except for the engine, a Merlin 266. The Merlin 266 was a low-altitude version of the Merlin 66 and was built under license in the USA by the Packard Motor Company.