UA 3913 then AA 3100 at Houston
Denver → Houston → Miami
Timetable, Houston time
21:22UA 3913 from Denver at the gate
09:49AA 3100 to Miami leaves the gate
12 h 27 apart on the timetable, overnight
AA 3100 leaves 12 h 27 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.