The Lockheed AC-130 gunship is a heavily armed, long-endurance, ground-attack variant of the C-130 Hercules transport, fixed-wing aircraft. It carries a wide array of ground-attack weapons that are integrated with sophisticated sensors, navigation, and fire-control systems. Unlike other modern military fixed-wing aircraft, the AC-130 relies on visual targeting. Because its large profile and low operating altitudes around 7,000 feet (2,100 m) make it an easy target, its close air support missions are usually flown at night. The airframe is manufactured by Lockheed Martin, while Boeing is responsible for the conversion into a gunship and for aircraft support. Developed during the Vietnam War as "Project Gunship II", the AC-130 replaced the Douglas AC-47 Spooky, or "Gunship I". The sole operator is the United States Air Force, which uses the AC-130U Spooky and AC-130W Stinger II variants for close air support, air interdiction, and force protection, with the upgraded AC-130J Ghostrider entering service. Close air support roles include supporting ground troops, escorting convoys, and urban operations. Air-interdiction missions are conducted against planned targets and targets of opportunity. Force-protection missions include defending air bases and other facilities. AC-130Us are based at Hurlburt Field, Florida, while AC-130Ws are based at Cannon AFB, New Mexico; gunships can be deployed worldwide. The squadrons are part of the Air Force Special Operations Command (AFSOC), a component of the United States Special Operations Command. The AC-130 has an unpressurized cabin, with the weaponry mounted to fire from the port side of the fuselage. During an attack, the gunship performs a pylon turn, flying in a large circle around the target, therefore being able to fire at it for far longer than in a conventional strafing attack. The AC-130H Spectre was armed with two M61 Vulcan cannons, one L/60 Bofors 40 mm cannon, and M137 cannon and M37 recoil mechanism from the M102 howitzer; after 1994, the cannons were removed. The upgraded AC-130U Spooky has a single GAU-12 Equalizer cannon in place of the Spectre's two cannons, an improved fire-control system, and increased ammunition capacity. The new AC-130J was based on the MC-130J Commando II special-operations tanker. The AC-130W Stinger II is a modified C-130H with upgrades including a precision strike package. Development Origins During the Vietnam War, the C-130 Hercules was selected to replace the Douglas AC-47 Spooky gunship (Project Gunship I) to improve mission endurance and increase capacity to carry munitions. Capable of flying faster than helicopters