AA 5510 then DL 825 at Atlanta
Washington National → Atlanta → Las Vegas
Timetable, Atlanta time
23:23AA 5510 from Washington National at the gate
20:42DL 825 to Las Vegas leaves the gate
21 h 19 apart on the timetable, overnight
DL 825 leaves 21 h 19 after AA 5510 arrives on the timetable: more than half a day, so not a connection we count.