The Curtiss H.16, the prototype of which appeared at the end of 1917, was the largest and most effective American maritime reconnaissance flying boat of World. War I. Heavily armed, and with a useful bomb load, the Curtiss H.16 was produced in substantial numbers; 150 were built by the Naval Aircraft Factory at Philadelphia, 77 of them for the US Navy with 400hp Liberty 12 engines. A further 125 H.16s were ordered for the RNAS, but 50 were cancelled and another 50 placed in storage in the UK. The remaining 25, delivered from 1918, saw service from coastal bases during the closing months of the war.