DL 9975 then UA 1074 at Boston
Miami → Boston → San Francisco
Timetable, Boston time
02:50DL 9975 from Miami at the gate
09:45UA 1074 to San Francisco leaves the gate
6 h 55 apart on the timetable
The last days
DL 9975 and UA 1074 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.