Aircraft Manufacturing Company Limited (Airco)
Airco DH.9A  Liberty
First flight July 1917

The Airco DH.9 (from de Havilland 9) – also known after 1920 as the de Havilland DH.9 – is a British single-engined biplane bomber that was developed and deployed during the First World War. The DH.9 was a development of Airco's earlier successful DH.4, with which it shared many components. These were mated to an all-new fuselage and the BHP/Galloway Adriatic engine, which promised increased performance. Anticipating its usefulness, the type was ordered in very large numbers for Britain's Royal Flying Corps (RFC).

To boost the rate of production, quantity orders for the DH.9 were also placed with Alliance, G & J.Weir, Short Brothers, Vulcan, Waring & Gillow and National Aircraft Factories No. 1 and No. 2. The first deliveries of the type occurred during November 1917 to 108 Squadron RFC; by the end of 1917, a total of five DH.9s had been delivered and passed their final inspections. The first combat engagement of the type, performed over France, was performed in March 1918 by No. 6 Squadron RNAS. By July 1918, a total of nine operational squadrons deployed to the Western Front were using the type.

Variants

• DH.9 – Revised version of the DH.4 with the pilot and observer/gunner placed closer together (3,024 production aircraft built with others built in Belgium and Spain).
• DH.9A – (also referred to as the Nine-Ack) was designed for Airco by Westland Aircraft to take advantage of the 400 hp (300 kW) American Liberty L-12 engine. Apart from the new engine and slightly larger wings it was identical to the DH.9. Initially it was hoped to quickly replace the DH.9 with the new version, but the shortage of Liberty engines available to the RAF limited the new type's service in the First World War, and it is best known as a standard type in the postwar RAF, serving as a general purpose aircraft for several years. 2,300 DH.9As were built by ten different British companies.
• DH.9B – Conversions for civilian use as three-seaters (one pilot and two passengers)
• DH.9C – Conversions for civilian use as four-seaters (one pilot and three passengers)
• DH.9J – Modernised and re-engined conversions using the 385 hp (287 kW) Armstrong Siddeley Jaguar III radial engine. Used by the De Havilland School of Flying.

• DH.9J M'pala I – Re-engined conversions carried out by the South African Air Force. Powered by a 450 hp (340 kW) Bristol Jupiter VI radial piston engine.
• M'pala II – Re-engined conversions carried out by the South African Air Force, powered by a 480 hp (360 kW) Bristol Jupiter VIII radial piston engine.
• Mantis – Re-engined conversions carried out by the South African Air Force, powered by a 200 hp (150 kW) Wolseley Viper piston engine.
• Handley Page HP.17 – A DH.9 experimentally fitted with slotted wings, tested 1920–1.
• USD-9/9A – DH.9s manufactured in the United States by the US Army's Engineering Division and Dayton-Wright. (1,415 ordered, only four built)^[