UA 3377 then AA 2151 at O'Hare
Pittsburgh → Chicago → Nashville
Timetable, Chicago time
08:30UA 3377 from Pittsburgh at the gate
20:50AA 2151 to Nashville leaves the gate
12 h 20 apart on the timetable
AA 2151 leaves 12 h 20 after UA 3377 arrives on the timetable: more than half a day, so not a connection we count.