Flight Incheon International Airport departs from Seoul Incheon International Airport at 12:05 and arrives at Kaohsiung International Airport at 13:55.
The flighttime is about 2h 50m. The distance travelled ("as the bird flies"): 1131 Km. So the average speed is roughly 399 Km.
There is an 1 hour time difference between Seoul and Kaohsiung