Flight Incheon International Airport departs from Seoul Incheon International Airport at 21:15 and arrives at Hong Kong Hong Kong International Airport at 00:05.
The flighttime is about 3h 50m. The distance travelled ("as the bird flies"): 1621 Km. So the average speed is roughly 423 Km.
There is an 1 hour time difference between Seoul and Hong Kong
The best day to arrive at Seoul is Friday and it would be best to avoid Monday, as prices are on average 91.92% higher than on Friday. (Average prices, based on 18013972 datapoints.)
We have a lot more statistics for flights KE 179 and between Seoul and Hong Kong.