Tethered Aerostats in the USA
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Currently the largest use of helium-filled aircraft by the government is for the Tethered Aerostat Radar System (TARS). Like the blimp bases of WWII, TARS stations exist on the periphery of the nation  though in this case, focused on the southern border, not the east and west coasts. There are currently eight active and three closed TARS stations on the continental USA, and one in Puerto Rico. The unmanned blimps are held aloft, two miles up, with a nylon cord, and contain radar equipment capable of seeing any aircraft or boat, within 200 miles. Mobile tactical radar aerostats are also used in warfare, and sometimes used to develop surveillance platforms elsewhere in the USA, and abroad.