Supermarine did not build any successive racing aircraft during this era, largely due to other commitments, including the development of a new fighter aircraft at the request of the British Air Ministry, known as the Type 224. Mitchell and his team's experience in designing high speed Schneider Trophy floatplanes greatly contributing to the development of the later Supermarine Spitfire, a fighter aircraft flown in large numbers by the Royal Air Force; it has been viewed as Britain's most successful interceptor of the Second World War. Both the Spitfire and its Rolls-Royce Merlin engine drew directly upon the S.6B and its Rolls-Royce R engine respectively.