<hi style=afpcap>The commercial Douglas Dolphin twin engined amphibian was readily adopted by the Army who needed a large capacity transport aircraft to supplement the Loenings then in service. Ten Y1C-21s were ordered in 1932, and were followed by the Y1C-26 which was essentially similar except for a different powerplant. The C-21s and C-26s were converted from the transport role to that of observation , changing designation to OA-3 and OA-4 respectively. </hi>
