Flight Gimpo International Airport departs from Seoul Gimpo International Airport at 13:05 and arrives at Jeju City International Airport at 14:20.
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 717.39% higher than on Tuesday. (Average prices, based on 815711 datapoints.)
We have a lot more statistics for flights 7C 121 and between Seoul and Jeju City.
