Rickenbacker's most lasting business endeavor was his longtime leadership of Eastern Air Lines. Through the 1920s, he had worked with and for General Motors (GM): first as the California distributor for its new car, the short-lived Sheridan, then later as a marketer for the LaSalle, and finally as vice president of sales for their affiliate, Fokker Aircraft Company. He persuaded GM to purchase North American Aviation, a conglomerate whose assets included Eastern Air Transport. GM asked him to manage Eastern, beginning in 1935. With the help of some friends, Rickenbacker merged Eastern Air Transport and Florida Airways to form Eastern Air Lines, an airline that eventually grew from a company flying a few thousand miles per week into a major airline. In April 1938, after learning that GM was considering selling Eastern to John D. Hertz, Rickenbacker met with GM's Chairman of the Board, Alfred P. Sloan, and bought the company for $3.5 million.  Rickenbacker oversaw many radical changes in the field of commercial aviation. He negotiated with the U.S. government to acquire air mail routes, a great advantage to companies in need of business. He helped develop and support new aircraft designs. Rickenbacker bought the new, large, faster airliners for Eastern Air Lines, including the four-engined Lockheed Constellation and Douglas DC-4. Rickenbacker personally collaborated with many of the pioneers of aviation, including Donald W. Douglas, the founder of the Douglas Aircraft Company, and the designer and builder of the large, four-engined airliners, the DC-4, DC-6, DC-7, and DC-8 (its first jet airliner).  Rickenbacker promoted flying to the American public, but, always aware of the possibility of accidents, he wrote in his autobiography, "I have never liked to use the word "safe" in connection with either Eastern Air Lines or the entire transportation field; I prefer the word 'reliable'."

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