Pan American World Airways, originally founded as Pan American Airways and commonly known as Pan Am, was an American airline that was the principal and largest international air carrier and unofficial overseas flag carrier of the United States for much of the 20th century.

During the 1970s, the title of "biggest" was often split between United Airlines for domestic volume and Pan American World Airways (Pan Am) for global reach. However, by most metrics of passenger miles and fleet influence, United Airlines was the largest carrier in the Western world, dominating the U.S. domestic market which was then the largest aviation market globally. Aeroflot, the state-owned airline of the Soviet Union, was technically the largest in the world by fleet size and passenger numbers, as it operated as a total monopoly across the USSR and its satellite states, but it was rarely compared directly with Western commercial carriers. In the 1970s, the "Big Four" in the U.S. (United, American, Delta, and Eastern) defined the industry. Pan Am remained the most iconic "biggest" international airline, serving as the unofficial flag carrier of the United States and pioneering the use of the Boeing 747 "Jumbo Jet," which revolutionized long-haul travel by drastically increasing the number of people who could be transported on a single flight.