B6 394 then AA 3748 at Boston
Denver → Boston → Washington National
Timetable, Boston time
18:05B6 394 from Denver at the gate
07:30AA 3748 to Washington National leaves the gate
13 h 25 apart on the timetable, overnight
AA 3748 leaves 13 h 25 after B6 394 arrives on the timetable: more than half a day, so not a connection we count.