The original (commercial production) 4-AT had three air-cooled Wright radial engines. It carried a crew of three: a pilot, a copilot, and a stewardess, as well as eight or nine passengers . The later 5-AT had more powerful Pratt & Whitney engines. All models had an aluminum corrugated sheet-metal body and wings. Unlike many aircraft of this era, extending through World War II, its control surfaces (ailerons, elevators, and rudders) were not fabric-covered, but were also made of corrugated metal. As was common for the time, its rudder and elevators were actuated by metal cables that were strung along the external surface of the aircraft. Engine gauges were also mounted externally, on the engines, to be read by the pilot while looking through the aircraft windshield. Another interesting feature was the use of the hand-operated "Johnny brake."