AA 4504 then UA 4559 at O'Hare
South Bend → Chicago → Knoxville
Timetable, Chicago time
18:35AA 4504 from South Bend at the gate
10:25UA 4559 to Knoxville leaves the gate
15 h 50 apart on the timetable, overnight
UA 4559 leaves 15 h 50 after AA 4504 arrives on the timetable: more than half a day, so not a connection we count.