Airco

During 1912, Airco was established by newspaper proprietor and industrialist George Holt Thomas. The firm was initially based at The Hyde in Hendon, north London, England. Starting in August 1914, the aviator William Taylor Birchenough worked as a test pilot for Airco. That same year, learning that Geoffrey de Havilland, who was then at the Royal Aircraft Factory in Farnborough, might be available, Holt Thomas invited him to join Airco as its chief designer. De Havilland's Airco designs would prove decisive to the company, which would eventually provide around 30 per cent of all trainers, fighters and bombers used by Britain and the United States during the First World War. De Havilland's designs for Airco were all marked with his initials "DH".

Wartime production

Airco would design and produce numerous aircraft during the wartime years. Its DH.2, a pusher configuration fighter introduced during 1916, contributed to ending the "Fokker scourge" of 1915. While early air combat over the Western Front had indicated the need for a single-seat fighter with forward-firing armament, there was no dominant approach to applying armaments to fighters at the time. As no means of firing forward through the propeller of a tractor aeroplane was available to the British, Geoffrey de Havilland designed the DH.2 as a smaller, single-seat development of the earlier two-seat DH.1 pusher design. A total of 453 DH.2s were produced by Airco.

Another design produced by de Havilland was the DH.6, which was specifically designed as a military trainer; as this role was normally performed by obsolete service types at the time, it was an unconventional choice to develop a dedicated trainer. The DH.6 possessed relatively gentle flying characteristics, being described as being probably the most "forgiving" aircraft of its time, allowing itself to be flown "crab wise" in improperly banked turns and able to maintain sustained flight at speeds as low as 30 miles per hour (48 km/h). At least 2,282 DH.6s were built in the UK during wartime.

The DH.4 was a two-seat combat aircraft, intended to perform both aerial reconnaissance and day bomber missions. By the end of production, a total of 1,449 aircraft (from orders for 1,700 aircraft) were constructed in Britain for the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS). Production of the DH.4 was performed by a variety of companies beyond Airco themselves; these included F.W. Berwick and Co, Glendower Aircraft Company, Palladium Autocars, Vulcan Motor and Engineering, and the Westland Aircraft Work. Overseas, SABCA of Belgium produced a further 15 DH.4s during 1926. In the United States, several different manufacturers, including the Boeing Airplane Corporation, Dayton-Wright Airplane Company, the Fisher Body Corporation, and the Standard Aircraft Corporation produced an Americanised variant of the DH.4, featuring over 1,000 modifications from the original British design, to equip the American air services.

During 1916, the DH.9 was designed as a successor to the DH.4, reusing both its wings and tail unit while adopting a modified fuselage that moved the pilot closer to the gunner/observer and away from the engine and fuel tank, which facilitated communication and was viewed as being a more optimal fighting configuration. However, While the DH.9 was deemed to be suitable for daytime bombing operations, it was found to be incapable of effective nighttime bombing due to the pilot's view being obstructed and visibility via the bombsight being unsuitable. The DH.9's performance in action over the Western Front was typically deemed to have been a disaster; heavy losses of the type were quickly incurred, attributed to both its poor performance and to engine failures, despite the prior derating of its engine to reduce the failure rate.