UA 3874 then AA 2840 at O'Hare
Chicago Rockford → Chicago → Philadelphia
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
15:21AA 2840 to Philadelphia leaves the gate
14 h apart on the timetable
AA 2840 leaves 14 h after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.