The Convair C-131 Samaritan is an American twin-engined military transport produced from 1954 to 1956 by Convair. It is the military version of the Convair CV-240 family of airliners. Design and development The design began life in a production requirement by American Airlines for a pressurized airliner to replace the Douglas DC-3. Convair's original design had two engines and 40 seats, and thus it was designated the CV-240. The first CV-240 flew on March 16, 1947, and production aircraft were first delivered to American on February 28, 1948. Seventy-five were delivered to American, with another fifty going to Western Airlines, Continental Airlines, Pan American Airways, KLM, Sabena, Swissair and Trans Australia Airlines. Operational history The CV-240/340/440 series was used by the United States Air Force (USAF) for medical evacuation and VIP transport and was designated as C-131 Samaritan. The first model Samaritan, the C-131A, was derived from the CV-240 model, and was delivered to the USAF in 1954. The initial trainer model, designated the T-29, was also based on the Convair CV-240 and was used to instruct USAF navigators for all USAF aircraft and United States Navy (USN) Naval Flight Officers (NFOs) selected to fly land-based aircraft. The 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. From 1952, the USN and United States Marine Corps (USMC) took delivery of 36 R4Y-1 transport aircraft similar to the commercial CV-340 and USAF C-131D, configured with 44 passenger seats and powered by a pair of Pratt & Whitney R-2800-52W engines. A single otherwise similar aircraft was acquired with a 24-seat VIP interior and designated R4Y-1Z. In 1957, the USN took delivery of two additional aircraft similar to the commercial CV-440 and designated R4Y-2. With the 1962 redesignation of USN/USMC aircraft, the three types were redesignated as the C-131F, VC-131F, and