Flight Gimpo International Airport departs from Seoul Gimpo International Airport at 10:10 and arrives at Jeju City International Airport at 11:25.
The flighttime is about 1h 15m. The distance travelled ("as the bird flies"): 271 Km. So the average speed is roughly 217 Km.
The best day to arrive at Seoul is Tuesday and it would be best to avoid Sunday, as prices are on average 385.7% higher than on Tuesday. (Average prices, based on 779567 datapoints.)
We have a lot more statistics for flights TW 707 and between Seoul and Jeju City.
