UA 3913 then AA 2357 at Houston
Denver → Houston → Phoenix
Timetable, Houston time
21:22UA 3913 from Denver at the gate
14:45AA 2357 to Phoenix leaves the gate
17 h 23 apart on the timetable, overnight
AA 2357 leaves 17 h 23 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.