The earlier trainer model, designated the T-29, was also based on the Convair 240 and was used to instruct USAF navigators for all USAF aircraft and those USN Naval Flight Officers (NFOs) selected to fly land-based naval aircraft. First deliveries to the USAF were made in 1950 followed by large production quantities until early 1955. The USAF and the USN operated T-29s in separate units at separate locations until 1976. In 1974, the USAF T-29s with the 323d Flying Training Wing (323 FTW) at Mather AFB, California began to be replaced by the Boeing 737-derived T-43. In 1975, the Navy retired all of its T-29s assigned to Training Squadron Twenty-Nine (VT-29) at NAS Corpus Christi, Texas, deactivated VT-29, and merged their advanced navigator training program for land-based NFOs with the Air Force's program at Mather AFB.
A planned bomber training version of the T-29 (designated T-32) was never built. The CV-340 model was used for most C-131Ds.
In addition to T-29 variants, the United States Navy used the Samaritan, initially designated as the R4Y until 1962, at which point the naval aircraft were also redesignated as C-131s.
Nearly all of the C-131s left the active USAF inventory in the late 1970s, but the U.S. Coast Guard operated the aircraft until 1983, while the Air National Guard and U.S. Navy units operated additional C-131 airframes, primarily as Operational Support Aircraft (OSA) for Air National Guard flying wings and as naval air station "station aircraft" until 1990. The C-131 was primarily replaced by the C-9 Nightingale in Regular USAF service, with the Air National Guard replacing their OSA with C-130 Hercules aircraft and the Navy with C-12 Hurons.
A Samaritan was the first aircraft used as a flying gunship testbed in mid-1963, in a program known as "Project Tailchaser". A C-131B (AF Ser. No. 53-7820) was given a gunsight for the side window, but instead of guns it had cameras in the cargo area. Eventually the C-131 was ferried to Eglin AFB in Florida and a General Electric SUU-11A/A 7.62 mm Gatling-style Minigun was installed. Live ammunition was used and both over-water and overland tests were successful.
Accidents and incidents
On 20 March 1956 a T-29B was destroyed near Dobbins AFB, Georgia, while en route from Harlingen Air Force Base, Texas, to Idlewild Airport in New York, killing 2, Capt Cecil Bryant and 1/Lt. Donald Carillo. It was the first fatal accident involving Harlingen personnel since the base was re-activated.
On 17 December 1960, a C-131D Samaritan crashed at Munich in what is the largest loss of life in an accident in the Bavarian capital. Shortly after takeoff one engine failed and the pilot tried to get back to Riem in heavy fog over Munich. Due to the limited visibility the aircraft struck the tip of St. Paul's church close to the Theresienwiese, and crashed onto a streetcar, killing all 20 people on board the plane, and 32 on the tram.
On 4 May 1970, a T-29 en route from Hamilton AFB, Novato, California, to Fairchild AFB, Washington, crashed on take-off in remote Sonoma County, killing 13 of 14 aboard.