AA 4504 then UA 4535 at O'Hare
South Bend → Chicago → Pittsburgh
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
12:48UA 4535 to Pittsburgh leaves the gate
18 h 13 apart on the timetable, overnight
UA 4535 leaves 18 h 13 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.