AA 4504 then UA 2371 at O'Hare
South Bend → Chicago → Cancún
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
08:40UA 2371 to Cancún leaves the gate
14 h 05 apart on the timetable, overnight
UA 2371 leaves 14 h 05 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.