Please be aware that Seoul has multiple airports and that these results are only for Gimpo International airport.
The best day to arrive at Seoul is Thursday and it would be best to avoid Friday, as prices are on average 150.38% higher than on Thursday. (Average prices, based on 381 datapoints.)
At Seoul the most flights depart around 08:00. (Hourly flights, based on 261 datapoints.)
From Seoul it is on average the cheapest to fly to Busan and to Shanghai. (Average prices, based on 240 datapoints.)
From Seoul most of the flights depart to Singapore, second best connected from Seoul is Tokyo. (Daily flights, based on 57 datapoints.)