Flight Incheon International Airport departs from Seoul Incheon International Airport at 18:45 and arrives at Tokyo Narita International Airport at 21:05.
The flighttime is about 2h 20m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 666 Km.
The best day to arrive at Seoul is Monday and it would be best to avoid Sunday, as prices are on average 160.43% higher than on Monday. (Average prices, based on 6880540 datapoints.)
We have a lot more statistics for flights KE 705 and between Seoul and Tokyo.
