Please be aware that Seoul has multiple airports and that these results are for all airports serving the city.
The best month to arrive at Seoul is November and the most expensive month to fly is October. (Average prices, based on 1795 datapoints.)
The best day to arrive at Seoul is Thursday and it would be best to avoid Saturday, as prices are on average 17.45% higher than on Thursday. (Average prices, based on 11697 datapoints.)
The cheapest airline flying to Seoul is Jeju Air. They are 74% cheaper than Korean Air. (Average prices, based on 1895 datapoints.)
At Seoul the most flights depart around 23:00. (Hourly flights, based on 2389 datapoints.)
From Seoul it is on average the cheapest to fly to Tokyo and to Manila. (Average prices, based on 358 datapoints.)
From Seoul most of the flights depart to Kuala Lumpur, second best connected from Seoul is Tokyo. (Daily flights, based on 267 datapoints.)