Designed in 1918 by Geoffrey de Havilland, the Airco DH.11 Oxford was developed for the Aircraft Manufacturing Company (Airco) as a replacement for the Airco DH.10 Amiens. Conceived as a twin-engined day bomber, the aircraft featured a three-bay biplane configuration with all-wood construction. The DH.11 was specifically engineered to utilize the ABC Dragonfly radial engine, a powerplant that was considered promising at the time but ultimately proved unsuccessful.
The aircraft's development was limited to a single prototype, which conducted its first flight in January 1919. Technical specifications for the prototype included a wingspan of 60 ft 2 in, a length of 45 ft 2 3/4 in, and a height of 13 ft 6 in. With a wing area of 719 sq ft, the aircraft had an empty weight of 4,105 lb and a maximum takeoff weight of 7,027 lb. The crew consisted of three members, and the aircraft was armed with two .303 in Lewis guns—one located at the nose and one at the midships position—along with internal capacity for four 230 lb bombs.
Power was provided by two ABC Dragonfly 9-cylinder air-cooled radial piston engines, each producing 320 hp. In flight tests, the DH.11 reached a maximum speed of 123 mph at sea level and 116 mph at an altitude of 10,000 ft. It possessed a service ceiling of 14,500 ft and could climb to 10,000 ft in 13 minutes and 45 seconds, with a total flight endurance of 3 hours.
Despite these specifications, the DH.11 never entered operational service. The prototype's poor performance, coupled with the failure of the ABC Dragonfly engines, led the British military to decline the purchase of the aircraft. Consequently, the project was abandoned in 1919, and all planned subsequent prototypes were cancelled. While Airco was a prominent wartime firm associated with de Havilland's early work, it is not the same entity as the later de Havilland Aircraft Company and is no longer in business. No examples of the DH.11 Oxford are known to have survived.