UA 4520 then AA 3974 at O'Hare
Northwest Arkansas → Chicago → Harrisburg
Timetable, Chicago time
09:33UA 4520 from Northwest Arkansas at the gate
08:27AA 3974 to Harrisburg leaves the gate
22 h 54 apart on the timetable, overnight
AA 3974 leaves 22 h 54 after UA 4520 arrives on the timetable: more than half a day, so not a connection we count.