Please be aware that Seoul has multiple airports and that these results are only for Gimpo International airport.
The best month to arrive at Seoul is April and the most expensive month to fly is September. (Average prices, based on 1275 datapoints.)
The best day to arrive at Seoul is Tuesday and it would be best to avoid Sunday, as prices are on average 56.84% higher than on Tuesday. (Average prices, based on 1158 datapoints.)
The cheapest airline flying to Seoul is Jeju Air. They are 88% cheaper than All Nippon Airways. (Average prices, based on 1303 datapoints.)
At Seoul the most flights depart around 08:00. (Hourly flights, based on 1355 datapoints.)