The first C-12A models entered service with the U.S. Army in 1974 and was used as a liaison and general personnel transport. The aircraft was essentially an "off-the-shelf" Super King Air 200, powered by the type's standard Pratt & Whitney Canada PT6A-41 engines.
The U.S. Navy followed suit in 1979, ordering a version of the Super King Air A200C (modified with a 52 inch by 52 inch cargo door from the Super King Air 200C), designating it the UC-12B, for logistics support between Naval and Marine Corps air stations, air facilities, and other activities, both in CONUS and overseas. The cabin can readily accommodate cargo, passengers or both. It is also equipped to accept litter patients in medical evacuation missions. Through 1982, the Navy ordered 64 of these aircraft.
A U.S. Air Force variant of the plane for surveillance roles primarily over Afghanistan and Iraq is the MC-12 Liberty. For that variant, Beechcraft builds the basic plane and then sends it to Greenville, Texas where sophisticated Intelligence, Surveillance & Reconnaissance equipment is installed by L-3 Communications Missions Integration. As of 2013 the Liberty program has exceeded 300,000 combat flying hours.
To meet the needs of transporting larger groups, the U.S. Army purchased six C-12J aircraft, based on the Beechcraft 1900C commuter airliner. One of the military C-12Js is used for GPS jamming tests at the 586th Flight Test Squadron, Holloman Air Force Base, New Mexico. Another is based at the 517th Airlift Squadron, Elmendorf Air Force Base, Alaska. Three were based at the 55th Airlift Flight, Osan Air Base, South Korea. They have been relocated to the 459th Airlift Squadron, Yokota Air Base, Japan. The remaining two are used by U.S. Army Aviation.
Although the UD- series 1900s were manufactured exclusively for military use, the United States military and other military and government organizations use 1900s from other series such as the UB-series 1900C, and 1900Ds which may be found elsewhere.
King Air 200-based variants
King Air 350-based variants
- MC-12W Liberty
Beechcraft 1900-based variant