Black helicopters is a term which became popular in the United States militia movement and associated political groups in the 1990s as a symbol and warning sign of an alleged conspiratorial military takeover of the United States, though it has also been associated with men in black and similar conspiracies. Rumors circulated that, for instance, the United Nations patrolled the US with unmarked black helicopters, or that federal agents used black helicopters to enforce wildlife laws. The concept may arise from the fact that many government agencies and corporations do use helicopters, and that some of these helicopters are dark-colored or black.