The C-21 is a twin turbofan-engine aircraft used for passenger and cargo airlift. The aircraft is the military version of the Learjet 35A business jet. In addition, the aircraft is capable of transporting one litter or five ambulatory patients for aeromedical evacuation operations. The C-21 can carry eight passengers and 42 cubic feet (1.26 cubic meters) of cargo. Fuel capacity of the C-21 is 931 gallons (3,537.8 liters) with refueling accomplished at ground level through each wingtip tank. Safety and operational capabilities of the C-21 are increased by the autopilot, color weather radar and tactical air navigation system as well as high-frequency, very high-frequency and ultra high-frequency radios.