UA 3870 then VS 1792 at San Francisco
Xiamen → San Francisco → Detroit
Timetable, San Francisco time
07:49UA 3870 from Xiamen at the gate
11:45VS 1792 to Detroit leaves the gatealso AF 2084
3 h 56 apart on the timetable
The last days
UA 3870 and VS 1792 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.