This plane, which was originally designed as a private venture, was the brainchild of R.J. Mitchell whose earlier S6 and S6B Seaplanes had won the SCHNEIDER Trophy for Britain. During its production life, some 40 variants of the Spitfire were made.

The Mk. IX depicted was intended as an interim type until the Mk. VIII became available, and was basically a Mk. Vc airframe using a Merlin 60 engine. This gave a top speed of 402 m.p.h.

A total of 5,600 Mk. IX's were produced and it became the most widely used variant of the Spitfire design. The Mk. IX entered service in July 1941 with 64 Squadron.

In January 1940, the British Government requested North American Aviation to build under licence another company's design. North American however, proposed a completely new fighter - the Mustang, producing the first prototype in 117 days.

Early machines entered service with the R.A.F. in July 1942 fitted with the Allison engine. Performance, excellent at low level, was not suitable for normal fighter operations and the aircraft were used on ground attack missions only.

Little interest was shown by the U.S.A.A.F. until the Rolls Royce Merlin 61 engine was successfully fitted as an experiment. An order for several thousand aircraft using Packard built Merlins followed, the P51.D. version becoming perhaps the best propeller driven fighter of W.W.2.

During the early part of World War II U.S. Navy observers learned many lessons particularly about ship board fighters. At this time the 'Wildcat' F3F was entering service and it was clear that in many respects it did not compare favourably with its contemporaries.

In June 1941 therefore an order was given to GRUMMAN to produce 2 prototypes of a more advanced machine. Weighing 60% more than the earlier fighter the new aircraft flew in June 1942 as the F6F-1. More speed was requested and the engine was changed to the more powerful R-2800-10 Double wasp.