So I have been looking at booking ORD-MCO on AA on flight 55. That flight is scheduled to depart ORD at 6:50pm. I have been reluctant to book due its horrible ontime percentage lately. I looked at today's flight and it shows delayed until 7:50pm. I clicked on the "incoming aircraft" link and the plane being used is coming from is AA2564 FLL-ORD. That flight shows a scheduled departure time of 4:45pm and scheduled arrival in O'Hare at 7:25pm. The 7:25pm arrival is an ontime arrival....35 minutes after the next flight is supposed to depart. How does this happen? I see why the ontime % is bad. Maybe AA is bad at math or this 737 has a time-machine button...but what gives?

All I can realistically think is the plane they were going to use went mechanical somewhere and this was the best they can do. I've seen this issue with this flight a few times though and am wondering if this leisure route is the first one to be thrown under the bus when a plane goes mechanical.

The only reason I really care is this flight might become a weekly flight for me and I want to get a sense if I should be looking at UA or SW.