UA 3909 then UA 863 at San Francisco
Houston → San Francisco → Sydney
Timetable, San Francisco time
07:17UA 3909 from Houston at the gate
23:05UA 863 to Sydney leaves the gatealso LX 3158, VA 8005, LH 9327, NZ 9863
15 h 48 apart on the timetable
UA 863 leaves 15 h 48 after UA 3909 arrives on the timetable: more than half a day, so not a connection we count.