The Boeing B-52 Stratofortress is a long-range, subsonic, jet-powered, strategic bomber operated by the United States Air Force (USAF) since 1955. The B-52A first flew in 1954, and the B model entered service in 1955. A total of 744 B-52s were built with the last, a B-52H, delivered in October 1962. It served in the Strategic Air Command, the Air Combat Command, and the B-52H continues to serve in the Air Force Global Strike Command and the Air Force Reserve Command. The B-52D models have the distinction of being the last bombers in aviation history to have shot down enemy aircraft during wartime with machine guns (tail gunners); two Vietnam War “MiG killer” bombers are currently preserved and on display at Fairchild AFB and the United States Air Force Academy. () Only the B-52H model is still active in the Air Force inventory. It is primarily assigned to the Air Force Global Strike Command and the Air Force Reserve Command, with one additional example in the Air Force Materiel Command supporting flight research operations with NASA. Australia B-52G 59-2596 2596 Darwin's Pride - Darwin Aviation Museum in Winnellie, Northern Territory. South Korea B-52D 55-0105 - War Memorial of Korea, Seoul, was operated by the 4258 SW at U-Tapao Royal Thai Navy Airfield in Thailand and the 96 BW at Dyess AFB, Texas. United Kingdom B-52D 56-0689 - Imperial War Museum Duxford, Duxford, England, was operated by the 28th BW and 7th BW at Carswell AFB. The B-52D is located in the American Air Museum building, alongside B-29A 44-61748 "It's Hawg Wild". B-52D 56-0689 is one of the largest and heaviest aircraft to have ever landed at the airfield. United States NB-52A 52-0003 - Pima Air & Space Museum adjacent to Davis-Monthan Air Force Base in Tucson, Arizona. It is a converted B-52A that was used by the Air Force Flight Test Center at Edwards AFB, California as the X-15 Launch Aircraft; now on display and marked as 0003 The High and the Mighty One. B-52B 52-0005 - under restoration at the Wings Over the Rockies Air and Space Museum (former Lowry AFB), Denver, Colorado. It is marked as "005 ", and was accepted on 3 March 1955. It was operated by the 6515th Maintenance Group (Air Research & Development Command) at Edwards AFB, 93rd BW / 330th BS at Castle AFB, 3415th MSG (ATC) at Lowry AFB, then redesignated as