UA 3874 then AA 1848 at O'Hare
Chicago Rockford → Chicago → Philadelphia
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
16:50AA 1848 to Philadelphia leaves the gate
15 h 29 apart on the timetable
AA 1848 leaves 15 h 29 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.