AA 9866 then UA 4791 at O'Hare
Marquette → Chicago → South Bend
Timetable, Chicago time
10:30AA 9866 from Marquette at the gate
10:25UA 4791 to South Bend leaves the gate
23 h 55 apart on the timetable, overnight
UA 4791 leaves 23 h 55 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.