The new type was ordered into production as a possible replacement for the Nieuport 17, but became “surplus” when it was decided to replace the Nieuport with the SPAD S.7 in the French air service. Some were supplied to the French Navy, a few of which were eventually passed to the U.S. Navy – some naval Hanriots were converted to, or built as, floatplanes with enlarged tail surfaces.
The bulk of early production, however, was diverted to the Belgians, who notoriously had to make do with aircraft unwanted by their allies. With the Belgian fighter squadrons the HD.1 proved surprisingly successful, and the type remained the standard Belgian fighter for the rest of the war. Willy Coppens, the top Belgian ace of the war was the most successful HD.1 pilot. At least one of his machines was experimentally fitted with an 11mm Vickers machine-gun for use in balloon busting, something which Coppens excelled at. Most of his victories were balloons and many were claimed while flying various HD.1s.
The type was also supplied in small numbers to the Italians who manufactured it in quantity, and used it to replace not only Nieuports but also SPADs in their service. The type was considered (by the Italians) to be a better all-round fighter than even the SPAD S.XIII and it became the standard Italian fighter, equipping 16 of the 18 operational Italian fighter squadrons by November 1918. Surplus Italian-built Hanriots were used by several countries postwar, including the Swiss.
The U.S. Naval Aircraft Factory built (or possibly modified/converted) 10 HD.1s in the immediate postwar years. These were mainly used as trainers, although they were also involved in experiments with takeoff platforms on warships – they could be fitted with twin guns, and at least one machine had a hydrovane and flotation bags of the type developed for the Royal Navy.