The date of the D.7's first flight is not known though it must have been after October 1917, when the Dreidekker was flying, and before May 1918 when a report from the Idflieg said the D.7 was about to recommence testing with the Mercedes engine.
The removal of the left-side gun is believed to have been pioneered on Oswald Boelcke's E.IV, believed to have borne IdFlieg serial 123/15, with a simpler double-synchronisation system used on the retained center-line and right side MG 08 Spandau guns.
On 8 April 1916, a novice German pilot took off from Valenciennes with a new E.III (IdFlieg serial number 210/16) bound for Wasquehal but became lost in haze and landed at a British aerodrome east of St. Omer.
It was first fitted to Leutnant Otto Parschau's Fokker A.III bearing IdFlieg military serial number A.16/15 in the late spring of 1915, to create the prototype of the entire line of Fokker Eindecker single-seat fighters to come.