USAir Flight 427 was a scheduled flight from Chicago's O'Hare International Airport to Palm Beach International Airport, Florida, with a stopover at Pittsburgh International Airport. On Thursday, September 8, 1994, the Boeing 737 flying this route crashed in Hopewell Township, Pennsylvania while approaching Runway 28R at Pittsburgh, which was at the time US Air's largest hub.

After the longest investigation in the history of the National Transportation Safety Board (NTSB), it was determined that the probable cause was that the aircraft's rudder malfunctioned and went hard over in a direction opposite to that commanded by the pilots, causing the plane to enter an aerodynamic stall from which the pilots were unable to recover. All 132 people on board were killed, making the crash the deadliest air disaster in Pennsylvania's history.