UA 3870 then CA 7336 at San Francisco
Xiamen → San Francisco → Seattle
Timetable, San Francisco time
07:49UA 3870 from Xiamen at the gate
12:22CA 7336 to Seattle leaves the gate
4 h 33 apart on the timetable
The last days
UA 3870 and CA 7336 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.