The AC-130s were fixed-wing gunships introduced to the Vietnam War in 1968. They were C-130 transport ships converted to AC-130s by
equipping them with two multibarreled machine guns, four 20mm Vulcan multibarreled guns and 40mm Bofors cannon, along with infrared
sensors, radar, low-light television, and laser target designators. The AC-130s were used both to provide ground support and to interdict
supplies being shipped along the Ho Chi Minh Trail.
And Other Vietnam War Short Stories
http://www.vietnamwar.net