For most of his flying career, Douin piloted the Dassault Mirage III and the Dassault Mirage 5, commanding a squadron, wing and fighter group, before becoming the French Air Attache to Pakistan and Chile.
After entering the General Ranks he served variously as a doctrinal specialist in the Air Force Staff & Training Command, the chief of Aerial Intelligence for a Fighter Division, and Commander of a Fighter Division.