UA 3876 then AA 4668 at O'Hare
Miami → Chicago → Louisville
Timetable, Chicago time
14:49UA 3876 from Miami at the gate
14:28AA 4668 to Louisville leaves the gate
23 h 39 apart on the timetable, overnight
AA 4668 leaves 23 h 39 after UA 3876 arrives on the timetable: more than half a day, so not a connection we count.