UA 3874 then AA 4993 at O'Hare
Chicago Rockford → Chicago → Milwaukee
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
17:24AA 4993 to Milwaukee leaves the gate
16 h 03 apart on the timetable
AA 4993 leaves 16 h 03 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.