AA 1838 then UA 3376 at O'Hare
Dallas-Fort Worth → Chicago → St Louis
Timetable, Chicago time
18:29AA 1838 from Dallas-Fort Worth at the gate
11:00UA 3376 to St Louis leaves the gate
16 h 31 apart on the timetable, overnight
UA 3376 leaves 16 h 31 after AA 1838 arrives on the timetable: more than half a day, so not a connection we count.