The Model S was Curtiss' first attempt at a fast and maneuverable single-seat fighter. The first variant, S-1, had disappointing performance. In March 1917, new wings were attached to the S-1 fuselage and the project was redesignated S-2. In 1917, the S-3 became the first triplane in service in the United States. In 1918 and 1919, Curtiss experimented with seaplane versions of the S-3, designated S-4 and S-5. The S-6 was intended to be an improved S-3, but performance was poor and of the 12 ordered by the USASC, only 1 was delivered.