The Westland Whirlwind entered service in 1940 and was one of the most advanced fighters of the time. It was twin-engined all-aluminium in construction, but still not much larger than a Hurricane. It was faster than the early Spitfire and highly-maneouverable at low altitude, and as all the guns were in the nose, it was an ideal interceptor and ground attack aircraft. The big problem for the Whirlwind however was the Rolls-Royce Peregrine engines. The development and production of the Peregrine was almost stagnant as Rolls-Royce were throwing all their weight behind the Merlin which was needed for Spitfires, Hurricanes, Lancasters, and Mustangs. These shortages meant that only 137 and 263 Squadrons were able to be equipped Whirlwinds, and when production of the Peregrine engine was halted, only 114 aircraft had been built.

It did see combat both as a fighter and fighter-bomber and was successful in both roles at low altitude only, as the Peregrine engine lacked the high-level performance of contemporary German fighters.

The Whirlwind was armed with 4 x 20mm cannon in the nose. The fighter-bomber could carry a single bomb under each wing. Trials of other armament configurations included a single 37mm cannon, and 12 x 7.7mm machine guns.