Please be aware that Seoul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Seoul and Manila is March and the most expensive month to fly is December. (Average prices, based on 1105 datapoints.)
The cheapest airline flying from Seoul to Manila is Cebu Pacific Air. They are 60% cheaper than Korean Air. (Average prices, based on 1113 datapoints.)
The best time to fly is at around 12. (Average prices, based on 1225 datapoints.)
NZD
