air national guard units are organized and federally recognized federal military reserve forces in each of the fifty u.s. states, the commonwealth of puerto rico, the territories of guam and the u.s. virgin islands, and the district of columbia of the united states. each state, the district of columbia and the commonwealth of puerto rico has a minimum of one ang flying unit with either assigned aircraft or aircraft shared with a unit of the active duty air force or the air force reserve under an "associate" arrangement. the ang of the territories of guam and the virgin islands have no aircraft assigned and perform ground support functions. air national guard activities may be located on active duty air force bases, air reserve bases, naval air stations/joint reserve bases, or air national guard bases and stations which are either independent military facilities or collocated as tenants on civilian-controlled joint civil-military airports.