UA 3905 then UA 1549 at Houston
Cancún → Houston → Washington
Timetable, Houston time
13:29UA 3905 from Cancún at the gate
07:22UA 1549 to Washington leaves the gate
17 h 53 apart on the timetable, overnight
UA 1549 leaves 17 h 53 after UA 3905 arrives on the timetable: more than half a day, so not a connection we count.