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 May. (Average prices, based on 2548 datapoints.)
The best day to arrive at Seoul is Wednesday and it would be best to avoid Friday, as prices are on average 19.71% higher than on Wednesday. (Average prices, based on 2576 datapoints.)
The cheapest airline flying to Seoul is Cebu Pacific Air. They are 40% cheaper than China Southern Airlines. (Average prices, based on 2658 datapoints.)
At Seoul the most flights depart around 23:00. (Hourly flights, based on 2797 datapoints.)
From Seoul it is on average the cheapest to fly to Shanghai and to Hong Kong. (Average prices, based on 757 datapoints.)
From Seoul most of the flights depart to Tokyo, second best connected from Seoul is Singapore. (Daily flights, based on 108 datapoints.)