UA 3501 then AA 3768 at O'Hare
Detroit → Chicago → St Louis
Timetable, Chicago time
06:57UA 3501 from Detroit at the gate
20:50AA 3768 to St Louis leaves the gate
13 h 53 apart on the timetable
AA 3768 leaves 13 h 53 after UA 3501 arrives on the timetable: more than half a day, so not a connection we count.