I'm sure things have changed, but as a starting point here are some top-10 2015 numbers from a 06 December 2016 article in USA Today about AA:
Busiest airports (by passengers, 2015)
1. Dallas/Fort Worth
2. Charlotte
3. Miami
4. Chicago O’Hare
5. Philadelphia
6. Phoenix
7. Los Angeles
8. New York LaGuardia
9. New York JFK
10. Washington Reagan National
Busiest airports (by scheduled departures, 2015)
1. Dallas/Fort Worth (284,223)
2. Charlotte (231,591)
3. Chicago O'Hare (165,279)
4. Philadelphia (156,456)
5. Miami (117,162)
6. Phoenix (100,968)
7. Washington Reagan National (84,832)
8. Los Angeles (66,076)
9. New York LaGuardia (54,617)
10. New York JFK (34,649)
https://www.usatoday.com/story/trave...bers/95014004/