[2] The D.IX was a single bay biplane, its wings constructed in Fokker's established fashion with two box spars and fabric covering.

[2] Its welded steel tube fuselage was flat sided, with the single seat open cockpit behind the trailing edge of the upper wing.

[2] The D.IX was sold to the US Army Air Service (USAAS) in 1922 and shipped to their experimental centre at McCook Field where they had earlier tried a variety of different engines in D.VIIs.

Instead of the original engine a locally built licensed version of the Hispano Type 42, the 320 hp (238 kW) Wright M-2 was fitted.

[1][3] They also fitted armament, two fixed 7.7 mm (0.303 in) machine guns in the upper engine cowling, firing through the propeller.