UA 2661 then UA 1531 at San Francisco
Philadelphia → San Francisco → Washington
Timetable, San Francisco time
09:22UA 2661 from Philadelphia at the gatealso NH 7021, CA 7299, VA 8451, NZ 9365
21:28UA 1531 to Washington leaves the gatealso CA 7312
12 h 06 apart on the timetable
UA 1531 leaves 12 h 06 after UA 2661 arrives on the timetable: more than half a day, so not a connection we count.