Appearing soon after the C.I, the prototype D.I single-seat fighter biplane bore little similarity to the reconnaissance aircraft and first flew with a 149kW Austro-Daimler engine installed. The two initial production versions entered service with the air arm and navy the same year as the D.I and D.II (balanced elevators), each powered by the 149kW Hiero engine and armed with two Schwarzlose machine-guns. Maximum speed was good, but the fighters had two faults - neither critical but nevertheless undesirable - being over-stable and structurally on the weak side.

As manoeuvrability was the very life-blood of fighters of 1917-18, a new version was produced in 1918 as the Type 9 or D.III which featured ailerons on all wings and was powered by a 171kW Hiero engine. The first of 158 built was supplied on 15 March 1918 and the last on 4 November 1918. It was undoubtedly the stability of the Phönix rather than its speed that led to a number of the earlier versions being used as photographic-reconnaissance aircraft. A number of D.Ills found their way into Swedish service after the war.