DL 9975 then DL 2275 at Boston
Miami → Boston → Washington National
Timetable, Boston time
02:50DL 9975 from Miami at the gate
14:28DL 2275 to Washington National leaves the gate
11 h 38 apart on the timetable
The last days
DL 9975 and DL 2275 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.