AA 3962 then DL 726 at Atlanta
Washington National → Atlanta → Boston
Timetable, Atlanta time
13:54AA 3962 from Washington National at the gate
13:50DL 726 to Boston leaves the gate
23 h 56 apart on the timetable, overnight
DL 726 leaves 23 h 56 after AA 3962 arrives on the timetable: more than half a day, so not a connection we count.