Lockheed's first major move towards becoming a significant manufacturer of transport aircraft came with design of the Lockheed 10 Electra. Providing accommodation for 10 passengers, the Electra was a cantilever low-wing monoplane of all-metal construction, with retractable tailwheel landing gear and a tail unit incorporating twin fins and rudders. Powered by two Pratt & Whitney Wasp Junior SBs, the prototype was flown for the first time on 23 February 1934, and was followed by 148 production aircraft. The Electra entered service during 1934, initially with Northwest Airlines, and in the late 1930s was used by eight American operators. By the time that the USA became involved in World War II, however, few remained in national airline service for the rapid growth in air travel had already shown these small-capacity aircraft to be uneconomical. In addition to those built for the home market, Electras were exported to Argentina, Australia, Canada, Chile, Colombia, Japan, New Zealand, Poland, Romania, USSR, UK, Venezuela and Yugoslavia. Small numbers also saw service in the Spanish Civil War and with the outbreak of World War II the type was impressed for service with the Royal Air Force and Royal Canadian Air Force. Use of the Electra by small civil operators continued after the war, as it was cheap to buy and operate, but few remained in service after the late 1960s.