AA 1637 then UA 1963 at Charlotte
Washington → Charlotte → Denver
Timetable, Charlotte time
08:38AA 1637 from Washington at the gate
08:36UA 1963 to Denver leaves the gate
23 h 58 apart on the timetable, overnight
UA 1963 leaves 23 h 58 after AA 1637 arrives on the timetable: more than half a day, so not a connection we count.