The nearest airport is in Incheon Intl. Airport (ICN), located 25.5 mi (41 km) from the city center. If you can't find a flight that works for your travel itinerary, you could also fly into Gimpo Intl. Airport (GMP), which is 5.6 mi (9.1 km) away.
Catch a ride on the metro at Dangsan Station for ease of access to the rest of the city.