Etienne Dormoy graduated in 1906 as an electrical engineer from Institut industriel du Nord (École Centrale de Lille, France).

He was then seconded to Maximilian Schmitt Aeroplane & Motor Works (Paterson, New Jersey), wherein he designed the first monocoque fuselage aircraft produced in the US.

Dormoy returned to France at the beginning of World War I, working for the Société Pour L'Aviation et ses Dérivés (SPAD).

In 1917, he joined the French industry delegation in the United States for SPAD technology transfer to Curtiss Aeroplane and Motor Company at Elmwood (Buffalo, New York).

After the war, Dormoy worked for the Engineering Division of the United States Army Air Service at McCook Field (Dayton, Ohio) from 1919 to 1925.