AA 4504 then UA 5869 at O'Hare
South Bend → Chicago → Sioux Falls
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
16:00UA 5869 to Sioux Falls leaves the gate
21 h 25 apart on the timetable, overnight
UA 5869 leaves 21 h 25 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.