AA 4504 then UA 4590 at O'Hare
South Bend → Chicago → Moline
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
12:40UA 4590 to Moline leaves the gate
18 h 05 apart on the timetable, overnight
UA 4590 leaves 18 h 05 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.