American Airlines on Monday operated its final flight with an Airbus A300 jet, retiring the model it pioneered more than two decades ago when it could not get Boeing 767s quickly enough to meet its needs. At one time, American flew 35 of the wide-body aircraft, but the airline has been phasing out the older planes as it trims capacity. American says the A300s eventually will be replaced with more fuel-efficient Boeing 787s, with initial deliveries slated for 2013.