American Airlines, known for its extensive network of hub airports, once operated a significant hub at St. Louis Lambert Airport (STL) in Missouri. The airline had expanded into STL after merging with Trans World Airlines (TWA) in the early 2000s, but the arrangement was short-lived.
In September 2009, American Airlines announced a shift in its route strategy, removing STL as a hub and strengthening other hubs such as Dallas/Fort Worth International Airport and Chicago O'Hare International Airport. This decision was primarily driven by a decline in travel demand following the September 11th attacks and the end of slot restrictions at O'Hare Airport in Chicago.
The carrier began reducing its presence at STL from 2003 onwards. Initially operating over 500 daily flights post-TWA acquisition, American Airlines reduced these to just over 200 by the end of 2003. By 2009, economic factors led to further cuts and ultimately resulted in closing STL as a reliever hub.