The MD-80, introduced by American in 1983, was at the time the quitest airliner in the skies. For over 20 years, it has formed the backbone of AA's short and medium haul fleet with over 140 examples in the skies. Though the 737-800 arrived to replace it in 1998, the "Mad Dog" has only begun being phased out in 2006-07. It is expected to continue in service through early in the next decade marking nearly 30 years service with American.