The first Boeing 727 flew in 1963 and for over a decade it was the most produced commercial jet airliner in the world. A total of 1,831 727s were delivered. The 727's sales record for the most jet airliners ever sold was broken in the early 1990s by its younger stablemate, the Boeing 737. In August 2008, there were a total of 81 Boeing 727-100 aircraft and 419 727-200 aircraft in airline service. These are constantly being replaced by more fuel-efficient Boeing 737s and Airbus A320-family aircraft.