UA 646 then AA 3292 at O'Hare
Portland (Maine) → Chicago → St Louis
Timetable, Chicago time
10:29UA 646 from Portland (Maine) at the gate
22:39AA 3292 to St Louis leaves the gate
12 h 10 apart on the timetable
AA 3292 leaves 12 h 10 after UA 646 arrives on the timetable: more than half a day, so not a connection we count.