Forerunner of the more than 8,000 Boeing jetliners built since its rollout May 14, 1954, the prototype of the KC-135 Stratotanker and the Model 707 jet transport was nicknamed the ''Dash 80.'' It served 18 years as a flying test laboratory before it was turned over to the Smithsonian Air and Space Museum in May 1972. In May 1990, under an arrangement with the Smithsonian, Boeing returned the airplane to Seattle for full restoration. It made a special flyover of the five Boeing facilities in the Puget Sound area on July 15, 1991, to commemorate the 75th anniversary of The Boeing Company and the 37 th anniversary of its own first flight. The airplane is now on view at Boeing Field in Seattle, Washington.