In the early 1960s, the Air Force began experimenting with fixed-wing, side-firing weapons systems for possible use in Vietnam. By 1964, the first gunship conversion of the World War Two Douglas C-47 Skytrain transport was completed under the Project Gunship I program. Basically, the C-47 was a military version of the famous Douglas DC-3 commercial airliner first pressed into service in 1936. During WWII, over 10,000 C-47s had been used in the war effort.
After the war, many planes continued to fly with the military. Many hauled supplies during the Korean conflict, as well as dropped paratroops, evacuated wounded, and other duties. By the time of Vietnam, the C-47 had been modified to to fly ground attack, reconnaisance and psychological warfare missions. This new version, equipped with three side-firing 7.62 Miniguns was nicknamed 'Puff the Magic Dragon'.
On December 15, 1964, the AC-47D, nicknamed 'Spooky' was first used in Southeast Asia. This was the plane flown with Larry Thornton acting as gunner and loadmaster on December 24, 1965, when Spooky #10 disappeared in Laos. the plane was an instant success providing ground support and soon more were added. The Fourth Air Commando Squadron was created in August 1965, with an 'EN' tailcode. 53 AC-47Ds were used in combat operations in Vietnam and Laos. The group had sixteen aircraft. Another group was added two years later. In 1968, the Air Commando units were renamed the Special Operations units. Although the plane was very successful as an attack aircraft, it was also vulnerable to enemy fire, and of the 53 Spookys that served, fifteen were shot down between December 1965 and September 1969.
Click HERE for a great video on Youtube of the AC 47 Spooky and its mission. Excellent action footage and information.