UA 3905 then UA 281 at Houston
Cancún → Houston → Denver
Timetable, Houston time
13:29UA 3905 from Cancún at the gate
09:40UA 281 to Denver leaves the gate
20 h 11 apart on the timetable, overnight
UA 281 leaves 20 h 11 after UA 3905 arrives on the timetable: more than half a day, so not a connection we count.