Beechcraft 1900 C-12J

In the US armed forces, C-12 Huron is the usual designation for military King Airs, derived from the Super King Air 200 and later the 350. The C-12J is the odd one out in the family: it does not come from a King Air but from the Beechcraft 1900C, the 19-seat regional airliner Beech had developed from the Super King Air. Jane's itself stresses the point, noting that the C-12 designation more properly belongs to the King Air. The C-12J should therefore not be confused with the King Air-based C-12 Hurons that make up the bulk of the series.

According to Jane's, the US Air Force ordered six Beech 1900C-1s in 1986, that is, the wet-wing version with integral tanks. Wikipedia's C-12 Huron article instead credits the purchase to the Army, explaining it by the need to carry larger groups than the King Airs could take. Both sources agree on the number: six aircraft. They were built exclusively for military use and given their own serial-number prefix, UD-1 to UD-6; that prefix being taken is why the later 1900Ds were numbered with UE.

The FAA type certificate data sheet (A24CE) lists the model as "1900C (C-12J)" in the same section as the civil 1900 and 1900C, with two Pratt & Whitney Canada PT6A-65B turboprops and a maximum operating altitude of 25,000 ft (7,620 m). In the fuel system, the UD aircraft share the tanks of the wet-wing UC series: two mains of 244.7 US gallons (about 926 l) and two auxiliaries of 93.3 US gallons (about 353 l). The six UD aircraft also have their own FAA-approved flight manual, 990-31475. The military configuration carries 2 crew and 19 passengers.

Jane's gives the initial distribution: four aircraft assigned to the Air Force's 3rd, 46th and 51st Wings (two to the last) for support duties, and two to the Army, one with headquarters in Europe and one with the 78th Aviation Battalion in Japan.

One C-12J became a unique test platform. The 586th Flight Test Squadron at Holloman Air Force Base, New Mexico, responsible for all Air Force flight testing over the White Sands Missile Range, added it to its fleet of highly modified AT-38Bs; according to GlobalSecurity it is the only test asset of its kind, used for Global Positioning System and inertial navigation tests, including GPS jamming trials. Another C-12J served with the 517th Airlift Squadron at Elmendorf Air Force Base, Alaska.

In South Korea, the 55th Airlift Flight at Osan Air Base operated three C-12Js. In November 2000 it completed its first-ever deployment: for 125 days, from Royal Australian Air Force Base Darwin, four members of the flight and two Raytheon maintenance contractors formed the 55th Expeditionary Airlift Flight in support of the joint US/UN humanitarian mission to East Timor. They flew the nearly daily four-hour round trip between Darwin and the austere Komoro airfield at Dili, carrying passengers and supplies. Those three aircraft later moved to the 459th Airlift Squadron at Yokota Air Base, Japan, where one was photographed landing on 29 June 2007.

Wikipedia states that the Air Force now operates only four C-12Js, three at Yokota with the 459th squadron and one with Air Force Materiel Command at Holloman, and that the Army also still has C-12Js in use. The designation is not limited to the six UD aircraft: it also covers other 1900Cs in US military service, and the armed forces additionally use 1900s from other series, such as UB-series 1900Cs, and 1900Ds. One example is 1900D 96-0112, which the Army received in March 1997 for the Chemical and Biological Defense Command at Aberdeen Proving Ground, an aircraft distinct from the C-12J even though Jane's lists it alongside.