The Bristol Pegasus is a British nine-cylinder single-row air-cooled radial engine. Used mainly for military aircraft in the 1930s and 1940s, Bristol reused the name many years later for the turbofan engine used in the Hawker Siddeley Harrier; that engine later became known as the Rolls-Royce Pegasus. Two Bristol Pegasus engines remain airworthy in 2009, powering Fairey Swordfish aircraft operated by the Royal Navy Historic Flight.