Designed to meet an American Airlines requirement for an enlarged version of the DC-2, the DC-3 was first flown on December 17th, 1935. Capable of carrying 24 passengers at a cruising speed of 180 mph, the DC-3's speed and long range revolutionized commercial air travel in the 1930s and 40s, when it carried 90 percent of the world's air travelers. Early DC-3s used Wright R-1820 Cyclone engines, but Pratt & Whitney R-1830 Twin Wasp Radials were fitted to later versions; these engines had better single engine performance and allowed the DC-3 to fly at higher altitudes.