Airco DH.4

DH.4
DH.4 above the clouds in France
Role	Light bomber / General purpose Type of aircraft
Manufacturer	Airco
Built by	Boeing Airplane Corporation Dayton-Wright Company Fisher Body Standard Aircraft Corporation
First flight	August 1916
Introduction	March 1917
Retired	1932 (United States Army Air Service)
Status	Retired
Primary users	Royal Flying Corps Royal Air Force Royal Naval Air Service United States Army Air Service
Number built	6,295, of which 4,846 were built in the United States.[1][2]
Variants	Airco DH.9 Airco DH.9A Dayton-Wright Cabin Cruiser

The Airco DH.4 is a British two-seat biplane day bomber of the First World War. It was designed by Geoffrey de Havilland (hence "DH") for Airco, and was the first British two-seat light day-bomber capable of defending itself.

It was designed and developed specifically as a bomber, as well as aerial reconnaissance missions. The DH.4 was to have been powered by the new 160 hp (120 kW) Beardmore Halford Pullinger (BHP) engine, but problems with that resulted in numerous other engines being used, perhaps the best of which was the 375 hp (280 kW) Rolls-Royce Eagle engine. The DH.4 first flew in August 1916 and it entered operational service in France on 6 March 1917 less than a year later. The majority were manufactured as general purpose two-seaters in the United States for the American expeditionary forces in France, becoming the only American made plane to see combat in WW1.

Following the Armistice of 11 November 1918, many DH.4s were sold to civil operators where it was found to be particularly useful as a mailplane. Early commercial passenger airplane service in Europe was initiated with modified variants of the DH-4. War-surplus DH-4s became key aircraft in newly emerging air forces throughout the world. The U.S. Army later had several companies re-manufacture its remaining DH.4s to DH.4B standard and they operated the type into the early 1930s.