The Martlet Mk IV was an export version of the American single-seat, carrier-based fighter-bomber Grumman F4F-4 Wildcat developed for the United Kingdom. A later modification of the F4F-3, it entered service with the U.S. Navy in 1939 and served as its primary carrier-based fighter until the Hellcat and Corsair arrived. In 1941, the United States sent 220 modified F4F-4Bs to the United Kingdom under the Lend-Lease program. These aircraft were distinguished by the installation of a less expensive Wright Cyclone R-1820-40B engine and a simplified air-cooling system. In England, the aircraft were adopted under the designation Martlet Mk IV. Martlets were in British service until the very end of the Second World War.

The Martlet Mk IV was introduced as one of the rewards for the 2018 “Good Old S.U.M.M.E.R” event. Though it sometimes lacks climb rate and straight-line speed, the Martlet Mk.IV is a good all-around fighter. Its strengths lie in its firepower, decent maneuverability, and excellent dive speed. Good pilot protection and overall structural strength help it withstand attacks. However, this variant differs from the American F4F-4 version in that it has a significantly lower service ceiling and poorer performance characteristics due to its underpowered engine.