the increasing importance of strategic vs. tactical missions eventually led to the end of the amst program in december 1979. then, in november 1979, the c-x task force formed to develop the required strategic aircraft with tactical capability. the c-x program selected a proposal for an enlarged and upgraded yc-15 and one prototype ("72-1875") was reclaimed from the pima air & space museum refurbished and returned to edwards afb, ca for flight testing that was later incorporated into development of the c-17 globemaster iii.