AA 2745 then UA 3876 at O'Hare
Las Vegas → Chicago → Miami
Timetable, Chicago time
23:35AA 2745 from Las Vegas at the gate
21:00UA 3876 to Miami leaves the gate
21 h 25 apart on the timetable, overnight
UA 3876 leaves 21 h 25 after AA 2745 arrives on the timetable: more than half a day, so not a connection we count.