The modern twin-engine 247 demonstrated new aerodynamic qualities. It was a low-wing, all-metal monoplane with retractable landing gear and powered by two 550-horsepower (410-kilowatt) Pratt & Whitney Wasp radial engines. Lightweight alloys reduced its weight. It had enough power to climb on one engine with a full load, and it was also the first airliner to use wing flaps. Its final version, the 247D, had variable-pitch propellers and improved performance at higher altitudes to compete with the Douglas DC-2. It had room for 10 passengers, two pilots, and a stewardess (as flight attendants were then called), plus mail and baggage.