UA 428 then UA 3917 at Houston
Mexico City → Houston → Austin
Timetable, Houston time
10:09UA 428 from Mexico City at the gate
07:30UA 3917 to Austin leaves the gate
21 h 21 apart on the timetable, overnight
UA 3917 leaves 21 h 21 after UA 428 arrives on the timetable: more than half a day, so not a connection we count.