UA 3913 then AA 5252 at Houston
Denver → Houston → Washington National
Timetable, Houston time
21:22UA 3913 from Denver at the gate
10:30AA 5252 to Washington National leaves the gate
13 h 08 apart on the timetable, overnight
AA 5252 leaves 13 h 08 after UA 3913 arrives on the timetable: more than half a day, so not a connection we count.