UA 3922 then AA 6487 at O'Hare
Savannah → Chicago → St Louis
Timetable, Chicago time
02:36UA 3922 from Savannah at the gate
15:18AA 6487 to St Louis leaves the gate
12 h 42 apart on the timetable
AA 6487 leaves 12 h 42 after UA 3922 arrives on the timetable: more than half a day, so not a connection we count.