Pacific Southwest Airlines (PSA) was a United States airline headquartered in San Diego, California, that operated from 1949 to 1988. 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 40 years." The airline initially operated as an intrastate air carrier wholly within California before expanding to other destinations in other states following the Airline Deregulation Act of 1978.