UA 3905 then UA 604 at Houston
Cancún → Houston → Philadelphia
Timetable, Houston time
13:29UA 3905 from Cancún at the gate
07:20UA 604 to Philadelphia leaves the gate
17 h 51 apart on the timetable, overnight
UA 604 leaves 17 h 51 after UA 3905 arrives on the timetable: more than half a day, so not a connection we count.