1,000-lb (454-kg) of mail, powered by a 410-hp (306-kW) Pratt & Whitney Wasp radial piston engine; seven built. Air Express Special One-off version built for Laura Ingalls , for a non-stop trans-Altantic flight in 1931; one built.   Specifications General characteristics Crew: 1 Capacity: 4 passengers or 100 cu ft (2.8m³) mail