From Air Transport World Statistics June Edition.Bear96 said:I think if you look at AA + Eagle as one entity, and UA + UAX as another, however, and compare the relative ASMs, the sizes would be much more similar.
Domestic Operations
Rank by RPM (Mainline only)
1. American 10,605,007
2. Delta 8,542,543
3. United 8,130,238
4. Southwest 5,574,905
Without adding their commuter carriers they are similar. Adding the commuters would probably not change the RPM's much.