AA 4504 then UA 399 at O'Hare
South Bend → Chicago → Baltimore
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
15:57UA 399 to Baltimore leaves the gate
21 h 22 apart on the timetable, overnight
UA 399 leaves 21 h 22 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.