<hi style=afpcap>For six years after the end of World War One the Army Air Service relied almost exclusively upon DH-4B and DH-4M biplanes for observation and light bombing duties. The Army soon realised it needed aircraft with a higher performance to perform these duties with eleven prototypes being evaluated. The Curtiss design was the O-1 which was constructed in a variety of version as the O-1 through O-1G, before production switched to the O-11, O-13, O-16, O-26 and O-39. The O-1B was developed as the A-3 in the attack role with a 0.30 inch gun mounted in the lower wing panel and two forward firing nose guns. In addition two Lewis guns were fitted to a Scarff ring in the rear cockpit. A total of 76 A-3s were built including five converted as trainers.</hi>
