AA 4504 then UA 4382 at O'Hare
South Bend → Chicago → Buffalo
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
10:30UA 4382 to Buffalo leaves the gate
15 h 55 apart on the timetable, overnight
UA 4382 leaves 15 h 55 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.