UA 4528 then AA 529 at O'Hare
St Louis → Chicago → Knoxville
Timetable, Chicago time
14:39UA 4528 from St Louis at the gate
10:36AA 529 to Knoxville leaves the gate
19 h 57 apart on the timetable, overnight
AA 529 leaves 19 h 57 after UA 4528 arrives on the timetable: more than half a day, so not a connection we count.