aircraft to Estonia, Djibouti, and Philippines. Civilian and Army National Guard service Several surplus aircraft were sold to United States operators, who used them to transport equipment and crews to remote work sites. Others were used by Army National Guard units in the various states. On 3 March 2001, a C-23B Sherpa belonging to the 171st Aviation Regiment of the Florida Army National Guard was carrying 18 construction workers of the Virginia Air National Guard from Hurlburt Field, Florida to Naval Air Station Oceana, Virginia. The pilot left the flight deck to use the aft bathroom. His weight in the tailcone shifted the center of gravity sufficiently that the airplane became unstable when a patch of severe turbulence was encountered. The violent g-force shifts then encountered rendered the crew unconscious and caused the breakup of the aircraft in flight near Unadilla, Georgia, killing the 21 persons on board. Later calculations determined that the aircraft had been loaded outside its operating envelope at the start of the flight. Variants C-23A Sherpa Twin-engine transport aircraft for the U.S. Air Force based on the Short 330-UTT; it was fitted with a strengthened cabin floor with a roller conveyor system, plus a forward cargo door on the port side of the fuselage, equipped with a hydraulically operated full-width rear cargo door/ramp; 18 built. C-23B Sherpa Twin-engine transport aircraft for the US Army National Guard, similar to the C-23A, but with cabin windows, stronger landing-gear, inward-opening paratroop doors at the rear of the fuselage and an air-operable two-section cargo ramp; 16 built. C-23B+ Super Sherpa Short 360 aircraft purchased as used aircraft by the U.S. Army and modified by the West Virginia Air Center (WVAC) for the replacement of the rear fuselage of the Short 360, with its single tall fin, with the twin tail and rear loading ramp of the Short Sherpa. 28 civil aircraft were modified. C-23C Both C-23B and C-23B+ with flightdeck avionic upgrade under the "Avionics System Cockpit Upgrade" program, 43 modified. C-23D C-23C with upgraded avionics under the "Safety Avionics Modification" program from 2010, program was cancelled and only four aircraft were modified. Operators Brazilian Army – Eight ex-ANG C-23B's acquired in 2016. Djibouti Air Force United States Air Force United States Army Army National Guard NASA United States Forest Service Civil operators Former USAF and US Army aircraft have been sold to civil operators including: Royal Star Aviation Era