example, operated its Carvairs in a flexible configuration, either accommodating five cars and 22 passengers or two-three cars and 55 passengers, permitting it to change over from one configuration to the other in about 40 minutes. In addition, the DC-4's lack of pressurisation made it ideal for low-altitude cross-Channel flights that did not go high enough to require a pressurised cabin. This made the proposed structural conversion straightforward. The result was a new aircraft christened Carvair (derived from car-via-air). Initially, it was thought that second-hand, pressurised Douglas DC-6 and Douglas DC-7 airframes could be converted into larger, "second generation" Carvairs within 15 years of the original DC-4-based Carvair's entry into service. The conversion of the original aircraft entailed replacing the forward fuselage with one longer, with a raised flightdeck in a bulbous "hump" (akin to the later Boeing 747) to allow a sideways hinged nose door. It also entailed more powerful wheel brakes and an enlarged tail, often thought to be a Douglas DC-7 unit, but actually a completely new design. The engines, four Pratt & Whitney R-2000 Twin Wasps, were unchanged. The prototype conversion first flew on 21 June 1961. Twenty-one Carvairs were produced in the UK, with production of aircraft 1, 11 and 21 at Southend Airport and the balance at Stansted Airport. The final three aircraft were delivered to Australia's Ansett-ANA, which supplied its own DC-4s to ATL for conversion, unlike the previous 18 aircraft that were purchased by ATL and either sold on or transferred to associate company British United Air Ferries (BUAF). One of the two aircraft still flying in June 2007 was an ex-Ansett airframe. A second Ansett aircraft was abandoned at Phnom Penh in 1975. The first flight of the last conversion, number 21, for Ansett, was on 12 July 1968. Basic price for a newly converted Carvair in 1960 was £150,000 (equivalent to £ million today), and based on the use of a C54 airframe, whilst only two of the three Ansett airframes supplied were of the DC4 variant. Operational history The Carvair was used by Aer Lingus, BUAF and BAF among others, and was used in Congo-Kinshasa during 1962–1963, under contract to the United Nations. Aircraft for Aer Lingus were quickly convertible between 55 seats and 22 seats with five cars. Some aircraft were pure freighters with only nine seats. One aircraft had 55 high-density seats and room for three cars.