Observation aircraft used by the United States Army Air Corps and USAAF. XO-46 was the first Douglas observation monoplane to be powered by a radial engine: a 725 hp Pratt & Whitney R-l535-7 fourteen-cylinder air-cooled radial driving a three-blade propeller. Plane have its wing braced to the fuselage by two parallel struts. OA-46A differed from the XO-46 in having their Pratt & Whitney R-1535-7 engines moved forward 21.6 cm to improve center of mass location and in having their canopies faired into the vertical fin. Plane entered service in 1936. Most of these were transferred to National Guard units in the late thirties and early forties, but a handful of 0-46As were still operated by the 2nd Observation Squadron at Nichols Field, Luzon, when Japan attacked the Philippines in December 1941 and these aircraft were the only Douglas observation monoplanes to see action, brief as it was.

Serials: XO-46: 33-291 O-46A: 35-161 - 35-231, 36-128 - 36-144 and 36-147 - 36-148 for NG

Source: René J.Francillon: McDonnell Douglas Aircraft since 1920: Volume I