UA 3874 then AA 6246 at O'Hare
Chicago Rockford → Chicago → Nashville
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
15:05AA 6246 to Nashville leaves the gate
13 h 44 apart on the timetable
AA 6246 leaves 13 h 44 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.