UA 3883 then B6 1187 at Boston
San Francisco → Boston → Los Angeles
Timetable, Boston time
08:16UA 3883 from San Francisco at the gate
20:30B6 1187 to Los Angeles leaves the gate
12 h 14 apart on the timetable
B6 1187 leaves 12 h 14 after UA 3883 arrives on the timetable: more than half a day, so not a connection we count.