Transcontinental Air Transport (T-A-T) was an airline founded in 1928 by Clement Melville Keys that merged in 1930 with Western Air Express to form what became TWA. Keys enlisted the help of Charles Lindbergh to design a transcontinental network to get government airmail contracts. Lindbergh established numerous airports across the country in this effort.
On July 7, 1929, transcontinental trips began. It initially offered a 48-hour coast-to-coast trip (trains by night, and planes by day in nine flights), with the first leg on the Pennsylvania Railroad overnight from New York City to Columbus, Ohio. There, passengers boarded a Ford Trimotor aircraft at what is now John Glenn Columbus International Airport and flew to Waynoka, Oklahoma. Then, passengers caught the Santa Fe Railway for an overnight trip to Clovis, New Mexico, where they would take a second Ford Trimotor flight to Los Angeles. One-way fare from New York to Los Angeles was $352.
Cynics were to deride its TAT abbreviation as “Take A Train.” – Source