Question: The Airco DH.9 was named after which British aviation pioneer?

full_context: Document 1: Airco DH.9A: The Airco DH.9A was a British single-engined light bomber designed and first used shortly before the end of the First World War. It was a development of the unsuccessful Airco DH.9 bomber, featuring a strengthened structure and, crucially, replacing the under-powered and unreliable inline 6-cylinder Siddeley Puma engine of the DH.9 with the American V-12 Liberty engine.
Document 2: Airco: The Aircraft Manufacturing Company Limited (Airco) was a British aircraft manufacturer operating from 1912 to 1920. Airco produced thousands of aircraft for the British military during the First World War, most of which were designed by their chief designer, Geoffrey de Havilland. Advertised in 1918 as the largest aircraft company in the world, Airco established the first airline in the United Kingdom, Aircraft Transport and Travel Limited, as a subsidiary. A glut of war surplus aircraft and a lack of government interest in aviation caused the company to become unprofitable, and in 1920 it was sold to Birmingham Small Arms Company, who had its operations liquidated later that year.
Document 3: De Havilland Mosquito: The de Havilland DH.98 Mosquito was a British twin-engine shoulder-winged multi-role combat aircraft. The crew of two, pilot and navigator, sat side by side. It served during and after the Second World War. It was one of few operational front-line aircraft of the era constructed almost entirely of wood and was nicknamed "The Wooden Wonder". The Mosquito was also known affectionately as the "Mossie" to its crews. Originally conceived as an unarmed fast bomber, the Mosquito was adapted to roles including low to medium-altitude daytime tactical bomber, high-altitude night bomber, pathfinder, day or night fighter, fighter-bomber, intruder, maritime strike aircraft, and fast photo-reconnaissance aircraft. It was also used by the British Overseas Airways Corporation (BOAC) as a fast transport to carry small high-value cargoes to, and from, neutral countries, through enemy-controlled airspace. A single passenger could ride in the aircraft's bomb bay when it was adapted for the purpose.
Document 4: Royal Aircraft Factory F.E.1: The Royal Aircraft Factory F.E.1 was designed and built in 1910 by the pioneer designer Geoffrey de Havilland. He used it to teach himself to fly during late 1910. After De Havilland was appointed assistant designer and test pilot at Army Balloon Factory at Farnborough (later the Royal Aircraft Factory) in December 1910 the War Office bought the aircraft for £400. the aircraft was given the designation F.E.1 ("Farman Experimental")
Document 5: De Havilland Mosquito operational history: The DH98 de Havilland Mosquito was the successor to the de Havilland DH.88 Comet, a twin-engined British aircraft designed for and winner of the 1934 MacRobertson Air Race between London and Melbourne (see De Havilland DH.88). The DH 98 served in many roles during and after the Second World War. Mosquito-equipped squadrons were asked to perform medium bomber, reconnaissance, tactical strike, anti-submarine warfare and shipping attack and Night fighter duties, both defensive and offensive, until the end of the war. Mosquitos were widely used by the RAF Pathfinder Force, which marked targets for night-time strategic bombing. Despite an initially high loss rate, the Mosquito ended the war with the lowest losses of any aircraft in RAF Bomber Command service. Post war, the RAF found that when finally applied to bombing, in terms of useful damage done, the Mosquito had proven itself 4.95 times more cost-efficient than the Lancaster.
Document 6: List of surviving de Havilland Mosquitos: The de Havilland DH.98 Mosquito was a British multi-role combat aircraft with a two-man crew that served with the Royal Air Force and other Allied countries during the Second World War and with many other air forces around the world in the postwar era. Only a few aircraft survive of almost 8,000 built. Three examples were airworthy as of September 2016.
Document 7: Alan Samuel Butler: Alan Butler (22 November 1898 —24 May 1987), full name Alan Samuel Butler, was (claimed his obituary in "The Times") the first private aeroplane owner-driver. From 1923 Butler was chairman of De Havilland Aircraft Company —which he financed— until 1950, a year when De Havilland employed 20,000 people and was building Comet, the world's first commercial jet airliner.
Document 8: De Havilland Comet: The de Havilland DH 106 Comet was the world's first commercial jetliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome, Hertfordshire, United Kingdom headquarters, the Comet 1 prototype first flew on 27 July 1949. It featured an aerodynamically clean design with four de Havilland Ghost turbojet engines buried in the wings, a pressurised fuselage, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and showed signs of being a commercial success at its 1952 debut.
Document 9: De Havilland Oxford: The Airco DH.11 was a British twin-engined biplane bomber which was designed to replace the earlier Airco DH.10 bomber. It was designed to use the unsuccessful ABC Dragonfly engine and was abandoned after the first prototype was built.
Document 10: De Havilland DH 108: The de Havilland DH 108 "Swallow" was a British experimental aircraft designed by John Carver Meadows Frost in October 1945. The DH 108 featured a tailless, swept wing with a single vertical stabilizer, similar to the layout of the wartime German Messerschmitt Me 163 "Komet" rocket-powered point-defence interceptor. Initially designed to evaluate swept wing handling characteristics at low and high subsonic speeds for the proposed early tailless design of the Comet airliner, three examples of the DH 108 were built to Air Ministry specifications E.1/45 and E.11/45. With the adoption of a conventional tail for the Comet, the aircraft were used instead to investigate swept wing handling up to supersonic speeds. All three prototypes were lost in fatal crashes.
Document 11: Airco DH.9: The Airco DH.9 (from de Havilland 9) – also known after 1920 as the de Havilland DH.9 – was a British single-engined biplane bomber developed and deployed during the First World War.
Document 12: Airco DH.2: The Airco DH.2 was a single-seat biplane "pusher" aircraft which operated as a fighter during the First World War. It was the second pusher design by Geoffrey de Havilland for Airco, based on his earlier DH.1 two-seater. The DH.2 was the first effectively armed British single-seat fighter and enabled Royal Flying Corps (RFC) pilots to counter the "Fokker Scourge" that had given the Germans the advantage in the air in late 1915. Until the British developed a synchronisation gear to match the German system, pushers such as the DH.2 and the F.E.2b carried the burden of fighting and escort duties.
Document 13: Geoffrey de Havilland: Captain Sir Geoffrey de Havilland (27 July 1882 – 21 May 1965) was a British aviation pioneer and aircraft engineer. His Mosquito has been considered the most versatile warplane ever built, and his Comet was the first jet airliner to go into production.
Document 14: Airco DH.4: The Airco DH.4 was a British two-seat biplane day bomber of World War I. It was designed by Geoffrey de Havilland (hence "DH") for Airco, and was the first British two-seat light day-bomber to have an effective defensive armament. It first flew in August 1916 and entered service with the Royal Flying Corps (RFC) in March 1917. The majority of DH.4s were actually built as general purpose two-seaters in the United States, for service with the American forces in France.
Document 15: Airco DH.5: The Airco DH.5 was a British First World War single-seat fighter aircraft designed to replace the obsolete Airco DH.2. It was one of the first British fighter designs to include the improved Constantinesco gun synchronizer, which allowed a forward-firing machine gun to fire through the propeller faster and more reliably than the older mechanical gears. It was also one of the earliest biplanes to feature a marked "back-stagger" of its wings. The DH.5 was inferior to other fighters already in production and proved unpopular and unsatisfactory in service. It was replaced as soon as supplies of the S.E.5a permitted.
ground_truth: Captain Sir Geoffrey de Havilland