High Quality Content by WIKIPEDIA articles! Pacific Southwest Airlines was a United States airline headquartered in San Diego, California, that operated from 1949 to 1988. It was one of the first large discount airlines in the United States and is considered a precursor to Southwest Airlines. PSA was known by its slogan "The World`s Friendliest Airline" and for the iconic smile painted on the nose of its airplanes, the PSA Grinningbirds... Opinion L.A. of the Los Angeles Times stated that PSA was "practically California`s unofficial in-state airline for almost 40 years."