UA 231 then AA 5447 at Charlotte
Denver → Charlotte → Washington
Timetable, Charlotte time
15:16UA 231 from Denver at the gate
15:12AA 5447 to Washington leaves the gate
23 h 56 apart on the timetable, overnight
AA 5447 leaves 23 h 56 after UA 231 arrives on the timetable: more than half a day, so not a connection we count.