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."
PSA was one of the four airlines that formed US Airways, the others being America West Airlines, Piedmont Airlines and Allegheny Airlines. US Airways merged with American Airlines in 2014.
PSA's Boeing customer number was 14. Following the acquisition by and merger with USAir (which was subsequently renamed US Airways), the PSA name was given by US Airways to Jetstream International Airlines to preserve the PSA name and trademarks.