Flight Gimpo International Airport departs from Seoul Gimpo International Airport at 15:55 and arrives at Jeju City International Airport at 17:05.
The flighttime is about 1h 10m. The distance travelled ("as the bird flies"): 271 Km. So the average speed is roughly 232 Km.
The best day to arrive at Seoul is Monday and it would be best to avoid Sunday, as prices are on average 191.62% higher than on Monday. (Average prices, based on 444052 datapoints.)
We have a lot more statistics for flights 7C 131 and between Seoul and Jeju City.