The C-130J's crew includes two pilots and one loadmaster (no navigator or flight engineer). The United States Marine Corps utilizes a crew chief for expeditionary operations. Its cargo compartment is approximately 41 feet (12.5 m) long, 9 feet (2.74 m) high, and 10 feet (3.05 m) wide, and loading is from the rear of the fuselage. The aircraft can also be configured with the "enhanced cargo handling system". The system consists of a computerized loadmaster's station from which the user can remotely control the under-floor winch and also configure the flip-floor system to palletized roller or flat-floor cargo handling. Initially developed for the USAF, this system enables rapid role changes to be carried out and so extends the C-130J's time available to complete taskings.
Lockheed Martin received the launch order for the J-model from the RAF, which ordered 25 aircraft, with first deliveries beginning in 1999 as Hercules C4 (C-130J-30) and Hercules C5 (C-130J). The standard C-130J had a flyaway cost of US$62 million in 2008.
In mid-June 2008, the United States Air Force awarded a $470 million contract to Lockheed Martin for six modified KC-130J aircraft for use by the Air Force and Special Operations Command. The contract led to C-130J variants that will replace aging HC-130s and MC-130s.
The HC-130J Combat King II personnel recovery aircraft completed developmental testing on 14 March 2011. The final test point was air-to-air refueling, and was the first ever boom refueling of a C-130 where the aircraft’s refueling receiver was installed during aircraft production. This test procedure also applied to the MC-130J Combat Shadow II aircraft in production for Air Force Special Operations Command.