AA 9866 then UA 4438 at O'Hare
Bloomington-Normal → Chicago → St Louis
Timetable, Chicago time
13:11AA 9866 from Bloomington-Normal at the gate
10:45UA 4438 to St Louis leaves the gate
21 h 34 apart on the timetable, overnight
UA 4438 leaves 21 h 34 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.