WS 6161 then UA 3906 at San Francisco
Mexico City → San Francisco → Washington
Timetable, San Francisco time
12:38WS 6161 from Mexico City at the gate
07:00UA 3906 to Washington leaves the gate
18 h 22 apart on the timetable, overnight
UA 3906 leaves 18 h 22 after WS 6161 arrives on the timetable: more than half a day, so not a connection we count.