The U.S. Air Force is replacing the aging LGM-30 Minuteman III intercontinental ballistic missile with the LGM-35A Sentinel ICBM to modernize the land-based leg of the U.S. nuclear triad. The Minuteman III ICBM have been operational since the early 1970s, and upon completion, the new Sentinel ICBM will maintain effective land-leg nuclear capabilities through 2075. The program will replace missile fields at the following air forces bases: F.E. Warren, Wyo., Malmstrom, Mont., and Minot, N.D.