Naval Air Station Jacksonville or NAS Jacksonville is a military airport located four miles (6 km) south of the central business district of Jacksonville, in Duval County, Florida, United States. Today, 23,000 civilian and active-duty personnel are employed on the base. The installation is considered to be one of the hubs for naval activity in the U.S. South. In addition to the many operational squadrons aboard, NAS Jacksonville is home to Patrol Squadron Thirty (VP-30), the Navy's largest aviation squadron and the only P-3C "Orion" Fleet Replacement Squadron that prepares and trains U.S. and NATO/Allied pilots, air crew and maintenance personnel for further operational assignments. NAS Jacksonville is also an Aviation Maintenance training facility for several aviation rates, facilitated by Center for Naval Aviation Technical Training Unit Jacksonville.