The U.S. Air Force is retiring its advanced cruise missile (ACM). This is a nuclear weapon, developed in the 1980s, to provide a stealthy (radar evading) cruise missile that could get past the Soviet air defense system radars. Air launched cruise missiles are carried by heavy bombers (B-52 and B-1). The air force was going to build 1,500 ACMs, but when the Cold War ended in 1991, production was cut short at about third of that number. There were also about 1,500 of the older, non-stealthy, air launched cruise missiles in service. These will apparently be the next to get retired. The early retirement of these weapons is driven largely by the nuclear disarmament treaties with Russia. These agreements call for both countries to reduce their nuclear arsenals to under 2,200 warheads. It's in the economic interest of both nations to do so, as it costs over a million dollars a year to maintain and guard a nuclear warhead, and 2,200 are more than enough to destroy whatever you want to destroy on this planet.