B6 1534 then DL 1574 at Boston
San Francisco → Boston → Washington National
Timetable, Boston time
06:44B6 1534 from San Francisco at the gate
10:45DL 1574 to Washington National leaves the gate
4 h 01 apart on the timetable
The last days
B6 1534 and DL 1574 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.