Pacific Southwest Airlines (PSA) was a regional U.S. airline headquartered in San Diego, California, that operated from 1949 to 1998. It was the first large discount airline in the United States. PSA called itself "The World's Friendliest Airline" and painted a smile on the nose of its airplanes, the PSA Grinningbirds. Opinion L.A. of the Los Angeles Times called PSA "practically the unofficial flag carrier airline of California for almost forty years."