The only full Air Force Base in the Hawaiian Islands, the 2,700-acre Hickam Air Force Base houses fighter and refueling aircraft and employs 6,400 personnel. Located on the edge of Honolulu International Airport, and adjacent to the Pearl Harbor Naval Shipyard, Hickam is engaged in supporting the Department of Defenses' operations within the Pacific Command area, which, although covering roughly half the earth's surface, is mostly water and small, nonmilitary islands. Other Air Force installations in the Hawaiian Islands include Bellows Air Force Station, offering recreation areas and amphibious training for the Marines, and a unit at the Kilauea Military Camp, which coordinates recreational activities on the Big Island. Hickam is part of a complex of over 75 military sites on Oahu, including several Air Force tracking and communication stations.