The nearest airport is in Incheon Intl. Airport (ICN), located 24.3 mi (39.1 km) from the city center. If you can't find a flight that's convenient for your trip, you might consider flying into Gimpo Intl. Airport (GMP), which is 6 mi (9.7 km) away.
Catch a ride on the metro at Guro Station for ease of access to the rest of the city.