The nearest airport is in Seoul (ICN-Incheon Intl.), located 30.2 mi (48.5 km) from the city centre. If you can't find a flight that works for your travel itinerary, you could also fly into Seoul (GMP-Gimpo Intl.), which is 11.1 mi (17.9 km) away.
Catch a ride on the metro at Sinbanpo Station for ease of access to the rest of the city.