UA 1535 then UA 3754 at Houston
Washington → Houston → Waco
Timetable, Houston time
15:27UA 1535 from Washington at the gate
11:30UA 3754 to Waco leaves the gate
20 h 03 apart on the timetable, overnight
UA 3754 leaves 20 h 03 after UA 1535 arrives on the timetable: more than half a day, so not a connection we count.