UA 4520 then AA 3484 at O'Hare
Northwest Arkansas → Chicago → St Louis
Timetable, Chicago time
09:33UA 4520 from Northwest Arkansas at the gate
09:30AA 3484 to St Louis leaves the gate
23 h 57 apart on the timetable, overnight
AA 3484 leaves 23 h 57 after UA 4520 arrives on the timetable: more than half a day, so not a connection we count.