Flight Incheon International Airport departs from Seoul Incheon International Airport at 16:55 and arrives at Tokyo Narita International Airport at 19:30.
The flighttime is about 2h 35m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 602 Km.
The best day to arrive at Seoul is Monday and it would be best to avoid Sunday, as prices are on average 117.49% higher than on Monday. (Average prices, based on 6879780 datapoints.)
We have a lot more statistics for flights KE 713 and between Seoul and Tokyo.
