Terminal A is the older terminal and is generally used by American Airlines flights that originate from the east coast of the United States. It is also used by some American Airlines flights that originate from the Gulf Coast.
Terminal B is the newer terminal and is generally used by American Airlines flights that originate from the west coast of the United States. It is also used by some American Airlines flights that originate from the Pacific Ocean. .
Overall, Terminal A is the older terminal and is generally used by American Airlines flights that originate from the east coast of the United States. Terminal B is the newer terminal and is generally used by American Airlines flights that originate from the west coast of the United States.
However, American Airlines does have flights that originate from both terminals and use the same aircraft.
Overall, I would say that Terminal A is the older terminal and is generally used by American Airlines flights that originate from the east coast of the United States.