AA 4615 then DL 1599 at Boston
Cincinnati → Boston → Washington National
Timetable, Boston time
20:13AA 4615 from Cincinnati at the gate
20:05DL 1599 to Washington National leaves the gate
23 h 52 apart on the timetable, overnight
DL 1599 leaves 23 h 52 after AA 4615 arrives on the timetable: more than half a day, so not a connection we count.