AA 3977 then UA 3376 at O'Hare
Detroit → Chicago → St Louis
Timetable, Chicago time
14:05AA 3977 from Detroit at the gate
11:00UA 3376 to St Louis leaves the gate
20 h 55 apart on the timetable, overnight
UA 3376 leaves 20 h 55 after AA 3977 arrives on the timetable: more than half a day, so not a connection we count.