UA 2180 then AA 3484 at O'Hare
Pittsburgh → Chicago → St Louis
Timetable, Chicago time
14:55UA 2180 from Pittsburgh at the gate
09:30AA 3484 to St Louis leaves the gate
18 h 35 apart on the timetable, overnight
AA 3484 leaves 18 h 35 after UA 2180 arrives on the timetable: more than half a day, so not a connection we count.