Pacific Southwest Airlines (PSA) Flight 182, registration N533PS, was a Boeing 727-214 commercial airliner that collided with a private Cessna 172 over San Diego, California on September 25, 1978. It was Pacific Southwest Airlines' first accident involving fatalities. The death toll of 144 makes it the deadliest aircraft disaster in California history. Until the crash of American Airlines Flight 191, it was also the deadliest plane crash in U.S.