AA 4504 then UA 3395 at O'Hare
South Bend → Chicago → St Louis
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
13:00UA 3395 to St Louis leaves the gate
18 h 25 apart on the timetable, overnight
UA 3395 leaves 18 h 25 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.