Flight Incheon International Airport departs from Seoul Incheon International Airport at 18:35 and arrives at San Francisco International Airport at 16:55.The flight has a short stop at Tokyo.
The flighttime is about 14h 20m. The distance travelled ("as the bird flies"): 12361 Km. So the average speed is roughly 862 Km.
There is an 16 hour time difference between Seoul and San Francisco