AA 4504 then UA 4572 at O'Hare
South Bend → Chicago → Sioux Falls
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
12:29UA 4572 to Sioux Falls leaves the gate
17 h 54 apart on the timetable, overnight
UA 4572 leaves 17 h 54 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.