AA 4504 then UA 3487 at O'Hare
South Bend → Chicago → Key West
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
10:58UA 3487 to Key West leaves the gate
16 h 23 apart on the timetable, overnight
UA 3487 leaves 16 h 23 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.