The KC-135 was the first offspring of the Dash 80. It was the only jet airplane designed specifically for aerial refueling and for 15 years was the only tanker used by the Strategic Air Command. The KC-135 replaced the propeller-powered KC-97 tankers, which could no longer keep up with the jet fighters and bombers. In 1956, when the first KC-135 -- nicknamed "The City of Renton" -- rolled out of the plant, it shared the Renton tarmac with the last KC-97, providing a vivid picture of The Boeing Company's complete conversion to jet power.