Flight Incheon International Airport departs from Seoul Incheon International Airport at 15:10 and arrives at Tokyo Narita International Airport at 17:50.
The flighttime is about 2h 40m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 583 Km.
The best day to arrive at Seoul is Monday and it would be best to avoid Sunday, as prices are on average 315.44% higher than on Monday. (Average prices, based on 6733809 datapoints.)
We have a lot more statistics for flights LJ 207 and between Seoul and Tokyo.
