AA 4504 then UA 745 at O'Hare
South Bend → Chicago → Boston
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
15:44UA 745 to Boston leaves the gate
21 h 09 apart on the timetable, overnight
UA 745 leaves 21 h 09 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.