The Air Line Pilots Association, International (ALPA) is the largest pilot union in the world, representing more than 77,000 pilots from 43 US and Canadian airlines. ALPA was founded on 27 July 1931 and is a member of the AFL-CIO and the Canadian Labour Congress. Known internationally as US-ALPA, ALPA is also a member of the IFALPA.

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 USAir's largest hub at the time.