DL 9975 then B6 733 at Boston
Miami (MIA) → Boston → San Francisco
Timetable, Boston time
02:50DL 9975 from Miami (MIA) at the gate
15:50B6 733 to San Francisco leaves the gate
13 h apart on the timetable
B6 733 leaves 13 h after DL 9975 arrives on the timetable: more than half a day, so not a connection we count.