Question: Clipper Cargo was a subsidiary cargo airline of  the principal and largest international air carrier in the United States that was founded in what year?

 Pan Am Cargo first used propeller aircraft just as the Douglas DC-4. Pan Am Cargo or Clipper Cargo was a subsidiary cargo airline of Pan American World Airways.  In 1963, Pan Am's all cargo jet service began in 1963 with Boeing 707-321C and it dominated Pan Am in air cargo market. <SEP> Air Wisconsin Airlines is a regional airline based at Appleton International Airport in the town of Greenville, Wisconsin, United States, near Appleton.  Air Wisconsin is the largest privately held regional airline in the United States.  It currently operates regional jet flights as American Eagle under contract to American Airlines via a code sharing agreement, serving cities in the U.S. and Canada with hubs at Boston Logan International Airport (BOS), Charlotte Douglas International Airport (CLT), Philadelphia International Airport (PHL) and Ronald Reagan Washington National Airport (DCA) .  Air Wisconsin previously operated United Express service on behalf of United Airlines followed by US Airways Express service on behalf of US Airways prior to becoming an American Eagle regional air carrier.  The company has announced it will once again partner with United Airlines as a United Express code sharing air carrier with primary hubs to be located at Chicago O'Hare International Airport (ORD) and Washington Dulles International Airport (IAD) beginning in September 2017 and will be "exclusively operating" as United Express by March 2018. <SEP> CJSC "Aeroflot-Cargo" (Russian: ЗАО «Аэрофлот-Карго» ) was a fully owned subsidiary of Aeroflot, founded on 26 October 2005 and incorporated on 19 April 2006.  It was the second largest cargo airline in Russia, behind Volga-Dnepr subsidiary AirBridge Cargo.  In June 2009 the shareholders of Russia's flagship air carrier, Aeroflot, decided to declare the company's cargo subsidiary, Aeroflot Cargo, bankrupt. <SEP>  Founded in 1927 as a scheduled air mail and passenger service operating between Key West, Florida, and Havana, Cuba, the airline became a major company credited with many innovations that shaped the international airline industry, including the widespread use of jet aircraft, jumbo jets, and computerized reservation systems.  It was also a founding member of the International Air Transport Association (IATA), the global airline industry association.  Identified by its blue globe logo ("The Blue Meatball"), the use of the word "Clipper" in aircraft names and call signs, and the white pilot uniform caps, the airline was a cultural icon of the 20th century.  In an era dominated by flag carriers that were wholly or majority government-owned, it was also the unofficial overseas flag carrier of the United States.  During most of the jet era, Pan Am's flagship terminal was the Worldport located at John F. Kennedy International Airport in New York City. Pan American World Airways, known from its founding until 1950 as Pan American Airways and commonly known as Pan Am, was the principal and largest international air carrier in the United States from 1927 until its collapse on December 4, 1991.