AA 4504 then UA 5941 at O'Hare
South Bend → Chicago → Tucson
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
15:35UA 5941 to Tucson leaves the gate
21 h apart on the timetable, overnight
UA 5941 leaves 21 h after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.