Originally Posted by mikesaidyes

You will NOT save time in a taxi at rush hour at that time. You will crawl along the entire length of the expressway. Same for a bus.

Instead, take Subway Line 9 EXPRESS train from Bongeunsa Station and you can arrive at Gimpo Airport in 35 minutes. Line 9 has two trains (All Stop) and (Express). Be sure to wait for the express train as All Stop will take double the time.

On the tv screen on the platform for the trains that are coming, All Stop is the green one, Express is the red train.

Line 9 can be very, very crowded in the mornings, so try to get a seat...then sit back and watch the show.