Armament consisted of a synchronized forward-firing Vickers machinegun and one or two Scarff-mounted Lewis machineguns on a Scarff ring on the rear cockpit. Normal bomb load consisted of two 230 lb (104 kg) bombs, but up to 660 lb (299 kg) could be carried on racks under the wings and fuselage.
A total of 2,300 aircraft were produced in Britain and thirteen in the USA by the following manufacturers:
The Aircraft Manufacturing Co., Ltd., Hendon
F. W. Berwick & Co., Ltd., London
Gloucestershire Aircraft Co. Ltd., Sunningend
Handley Page Ltd., Cricklewood
H. G. Hawker Engineering Co. Ltd., Kingston upon Thames
Mann, Egerton and Co. Ltd., Norwich
George Parnall and Co. Ltd., Yate
S. E. Saunders Ltd., East Cowes
Short Bros. Ltd., Rochester
The Vulcan Motor and Engineering Co. Ltd., Southport
Westland Aircraft Works, Yeovil
Whitehead Aircraft Co. Ltd., Richmond
The Dayton-Wright Airplane Co., Dayton, Ohio, USA
The Engineering Division of the USAAS, Dayton, Ohio, USA
Deliveries of the initial aircraft soon commenced, equipping No. 110 (Hyderabad) Squadron which reached France on August 31 to become part of the Independent Force. Only five raids were made, starting on September 14, before the Armistice. No. 205 Squadron was the only other unit to use D.H.9As on active service and other squadrons were beginning to receive new aircraft. In the USA, production of 4,000 D.H.9As was planned, but with the end of hostilities in Europe only thirteen modified examples were completed. However, the D.H.9A did become the standard RAF day bomber, serving for many years both at home and in overseas territories as far away as India for policing duties, ending its career as initial equipment of the Auxiliary Squadrons and as an advanced trainer.
With the cessation of hostilities in Europe, the RAF D.H.9A units became part of Allied Occupation Force, mainly on communication duties, but were soon disbanded. In 1919 eleven aircraft were re-engined with a 450 hp Napier Lion or 465 hp Lion II engine for trials. Six of the Lion II-powered aircraft came on the civil registry on October 9, 1919 and were used by Aircraft Transport & Travel Ltd. on the air mail service to the Army of Occupation on the Rhine in Germany; by June 1920 these six had been returned to the RAF.
Most of the day bomber squadrons were based overseas on active duties on the infamous North West Frontier in India, supporting the White Russians against the Bolsheviks and operating in Greece against Turkey. Policing duties in the Near and Middle East included the vast featureless areas of Iraq (then Mesopotamia) where four D.H.9A squadrons were based and used on active duty, as well as communications which helped to prove the routes for future commercial air transport. D.H.9As also played a vital part in the evacuation of the British Legation under siege at Kabul in Afghanistan in extremely bad weather conditions in December 1928. The last of the venerable 'Ninaks', as they were known, was retired from active duties in April 1930, and by the end of the year they had also been retired from the UK-based Auxiliary Squadrons.
The pictured aircraft was produced by Westland and first flew at Yeovil on October 2, 1918."