AA 4125 then UA 3876 at O'Hare
Washington National → Chicago → Miami
Timetable, Chicago time
23:44AA 4125 from Washington National at the gate
21:00UA 3876 to Miami leaves the gate
21 h 16 apart on the timetable, overnight
UA 3876 leaves 21 h 16 after AA 4125 arrives on the timetable: more than half a day, so not a connection we count.