The Jetstar originated as a private project within Lockheed, with an eye to winning a USAF requirement that was later dropped due to budget cuts. Lockheed decided to continue the project on their own for the business market. The first two prototypes were equipped with two Bristol Siddeley Orpheus engines, the first of these flying on 4 September 1957. Lockheed attempted to arrange a contract to produce the Orpheus locally in the US, but when these negotiations failed they re-engined the second prototype, N329K, with four P&W JT12 in 1959. The JT12 fit proved successful and was selected for the production versions, the first of which flew in mid 1960.These versions entered commercial service in 1961. Sixteen Jetstars were produced for the USAF Five C-140A Flight Inspection aircraft to perform airborne testing of airport navigational aids in 1962. They began service during the Vietnam War and remained in service until the early 1990s. The "Flight Check" C-140A were a combat-coded aircraft that could be distinguished from the VIP transport version by their distinctive camouflage paint scheme. The last C-140A to be retired was placed on static display at Scott AFB, Illinois, to honor its distinguished service. In addition 11 airframes were designated C-140B, although the first of these predated the C-140As when it was delivered in 1961. The C-140Bs were used to transport personnel by the Military Airlift Command. Six of the aircraft were operated as VIP transports by the 89th Military Airlift Wing at Andrews Air Force Base, near Washington DC. These VIP aircraft were designated as VC-140Bs. The VIP transport fleet occasionally served as Aircraft One during the 1970s and 1980s. Several other countries have used military Jetstars as transports for their VIP persons. Noise regulations in the US and high fuel consumption led to the development of the 731 Jetstar, a modification program which added new Garrett AirResearch TFE731 Turbofan engines and redesigned external fuel tanks to original Jetstars. The 731 Jetstar modification program was so successful that Lockheed produced 40 new Jetstars, designated the Jetstar II, from 1976 through 1979. The Jetstar IIs were factory new aircraft with the turbofan engines and revised external fuel tanks. Both 731 Jetstars and Jetstar IIs have greatly increased range, reduced noise, and better runway performance compared to the original Jetstars. Jetstar production totaled 204 aircraft by final delivery in 1978.