Korean Air: Transit Exclusive Domestic Flights

Korean Air has a set of flights that between ICN and Busan/Daegu that allow you to do immigration at Busan/Daegu instead of Incheon

https://www.koreanair.com/contents/booking/reservation-guide/how-to-book/domestic-transit?hl=en#:~:text=1400 series domestic-transit?hl=en#:~:text=1400%20series