The DH9 was designed as a fast bomber to carry heavier loads over greater distances than the DH4. Using the manufacturing facilities for the well proven DH4, the DH9 had the same mainplanes and tail surfaces, but with a new fuselage placing the pilot and gunner close to each other, rather than separated by the fuel tank as on the DH4!
Early DH9s suffered from engine problems, resulting in initial aircraft having a lower performance than the DH4. Eleven other types of engine were eventually fitted to DH9 variants. Post war, the DH9 was rapidly replaced in RAF service by the much more successful DH9A. However, many were supplied to other nations for both military and civil uses, with at least one still active in Spain in 1940.