American Airlines Inc., a unit of AMR Corp. , said Wednesday it has accelerated its fleet renewal plan by beginning the replacement process for part of its MD-80 fleet. American said it has notified Boeing Co. of its plans to begin pulling forward the delivery of 47 Boeing 737-800 aircraft under a previously existing purchase agreement. Fort Worth, Texas-based American said it has informed Boeing that the airline will take delivery in early 2009 of three 737s previously scheduled for delivery in 2016. In addition, American said it plans to continue pulling forward deliveries of the other 737s from their current 2013-2016 delivery schedules into the 2009-2012 timeframe.