Shortly after World War I, Supermarine received two Air Ministry contracts, one in 1921 for a five-seat military seaplane and the other in 1922 for a commercial seaplane, the former named Scylla and the latter Swan. The Scylla emerged as a monoplane, but was apparently converted to triplane configuration in 1923, when it carried out taxi trials at Felixstowe. There is no evidence that it ever flew. The Swan was completed as planned in 1924, but as a maritime reconnaissance flying-boat biplane. After completing its flight trials, it was converted to civilian use.