Bingo! ORD alone is probably responsible for a big chunk of AA's on-time deficit, and I avoid it whenever possible, even if it means extra time or connections. Of course, UA also has a mega-hub at ORD and somehow manages to do better. That's where t-storms at DFW and ATC and ground congestion at other places demkr mentions come into play.

Could AA do better through operational adjustments? I'm pretty sure they could, but only up to a point. And I don't mean more padding of the schedule. AA and DL, while not the only ones, do this to a really large extend and still always seem to rank in the bottom of the rankings. To add insult to injury, my own experience at DL was that, on those occasions when they got their act together operationally at one end, we would be early arriving into ATL and have to wait as much as forty minutes for a gate.

Ah the joys of flying through overworked hubs!