Seoul Gimpo to Jeju island is one of the most frequent domestic corridors around the world, however, the largest Korean airport and also in the Seoul area, Incheon have zero direct flight to Jeju. I am curious about this as transferring from Incheon to Gimpo would require me to obtain a Korean Visa as a Chinese National while Jeju island has visa waivers for Chinese. If there is a flight from ICN-CJU flight, I can travel to Jeju on Korean Air from SIN instead of flying direct on Scoot for 6 hours without the need of getting a Visa.