UA 3901 then UA 5548 at Houston
Phoenix → Houston → Washington National
Timetable, Houston time
09:39UA 3901 from Phoenix at the gate
09:32UA 5548 to Washington National leaves the gate
23 h 53 apart on the timetable, overnight
UA 5548 leaves 23 h 53 after UA 3901 arrives on the timetable: more than half a day, so not a connection we count.