Convair CV - 240 family The Convair CV - 240 was an American airliner produced by Convair from 1947 to 1954 , initially as a possible replacement of the ubiquitous Douglas DC - 3 . While featuring a more modern design , the 240 series was able to make some inroads as a commercial airliner and also had a long development cycle which resulted in a number of civil and military variants . Although reduced in numbers through attrition , the " Convairliners " in various forms continue to fly into the 21st century . Design and development . The design began life in a requirement by American Airlines for an airliner to replace its Douglas DC - 3 s . Convair ' s original design , the unpressurised Model 110 was a twin - engined low - wing monoplane of all - metal construction , with 30 seats . It was powered by Pratt & Whitney R - 2800 Double Wasp radial engines and had a tricycle landing gear and a ventral airstair for passenger boarding . The prototype Model 110 , registration " NX90653 " first flew on July 8 , 1946 . By this time , American had changed their requirements to require pressurization and deemed the design too small . The first prototype was used by Convair for development work for the 240 series before being broken up in 1947 . To meet the requirements of airlines for a pressurized airliner Convair produced a revised design , the Model 240 . This had a longer but thinner fuselage than the Model 110 , accommodating 40 passengers in the first pressurized twin - engined airliner . The 240 first flew on March 16 , 1947 . The Model 240 was followed by the Model 340 that had a longer fuselage , longer - span wings and more powerful engines . The 340 first flew on October 5 , 1951 . In 1954 , in an attempt to compete with turboprop - powered airliners like the Vickers Viscount , Convair produced the Model 440 Metropolitan , with more streamlined cowlings , new engine exhausts and better soundproofing for the cabin . As the " Super 240 " evolved into the CV - 340 and CV - 440 , the limit of piston - engine performance was reached , and future development centered on conversion to turboprop power . Operational history . The first delivery of a production Convairliner was to American on February 29 , 1948 . A total of 75 were delivered to American , with another 50 going to Western Airlines , Continental Airlines , Pan American Airways , KLM , Swissair , Sabena and Trans Australia Airlines . A CV - 240 was the first private aircraft used in a United States presidential campaign . In 1960 , John F . Kennedy used a CV - 240 named " Caroline " ( after his daughter ) during his campaign . This aircraft is now preserved in the National Air and Space Museum . After aborted negotiations with TWA and Eastern for " Super 240 " orders , the production of the 240 series was temporarily halted . In response to a United inquiry , however , Convair redesigned the Super 240 , calling it the CV - 340 . United ordered 55 , and more US orders came from Braniff , Continental , Delta , Northeast and National . Other orders came from abroad , and the CV - 340 proved popular in South America . The CV - 340 earned an enviable reputation for reliability and profitability , and was developed into the CV - 440 Metropolitan , the final piston - engined variant of the " Convairliners . " Kelowna Flightcraft Air Charter , the major remaining operator of this model , currently holds the type certificate for this aircraft . Used price for a Convair 240 in 1960 was around £40 , 000 . Variants . " Data from : " General Dynamics Aircraft and their Predecessors