AA 1997 then DL 1556 at O'Hare
St Louis → Chicago → Los Angeles
Timetable, Chicago time
09:00AA 1997 from St Louis at the gate
07:45DL 1556 to Los Angeles leaves the gate
22 h 45 apart on the timetable, overnight
DL 1556 leaves 22 h 45 after AA 1997 arrives on the timetable: more than half a day, so not a connection we count.