TWA was formed on July 16, 1930, in the amalgamation of divisions of Western Air Express (founded 1925) and Transcontinental Air Transport (founded 1928). Western Air Express had flown both mail and passengers in its first year of service between Los Angeles and Salt Lake City, Utah (1926), and in 1930 TWA inaugurated coast-to-coast service from Newark, New Jersey, to Los Angeles in 36 hours with a stopover in Kansas City, Missouri. In 1934 Western Air Express again became independent (later to be called Western Air Lines), but TWA continued as a transcontinental airline.

Until 1950 it was known as Transcontinental & Western Air, Inc.

In 1946, TWA inaugurated international flights between New York City and Paris, quickly expanding by the 1950s to routes through Europe, the Middle East, Africa, and Asia. From 1969 to 1975 it operated transpacific services and was a round-the-world carrier, but in 1975 it suspended such services in a route exchange with Pan American World Airways.

The financier and aviation pioneer Howard Hughes was the principal stockholder and guiding genius of TWA from 1939 until 1960–61, when he lost control of the airline to a group of Wall Street banks and financial institutions that had financed the purchase of jet aircraft for the airline. An antitrust suit was mixed in with the complex civil litigation, and the multiple litigation involved repeated court hearings, before which the reclusive Hughes refused to appear. In 1966 he sold his TWA shares for more than $500 million.

TWA reorganized under the ownership of a holding company called Transworld Corporation in 1979, but Transworld sold TWA to the public in 1984 in the course of defending itself against a threatened hostile takeover. By then TWA was experiencing financial troubles, and in late 1985 the American investor Carl C. Icahn acquired the airline. In 1986 TWA bought Ozark Air Lines, Inc., a carrier with routes centred on the south-central United States.

Although it continued to operate as usual, the company filed for bankruptcy (to enable timely reorganization) in 1992. Despite emerging from bankruptcy the following year, TWA continued to operate at a loss and announced in January 2001 that American Airlines would acquire its assets. TWA ceased to exist as a separate airline in December 2001.