AA 9866 then UA 3556 at O'Hare
Bloomington-Normal → Chicago → St Louis
Timetable, Chicago time
13:11AA 9866 from Bloomington-Normal at the gate
08:55UA 3556 to St Louis leaves the gate
19 h 44 apart on the timetable, overnight
UA 3556 leaves 19 h 44 after AA 9866 arrives on the timetable: more than half a day, so not a connection we count.