With the opening of Gimhae-Busan LRT, Korea had fourth railway line linked with an airport. Concretely speaking, it was linked with Gimhae International Airport.
You can access to the downtown of Busan by taking Gimhae-Busan LRT and changing trains at Daejeo or Sasang.
But, judging from the fact that Gimhae-Busan LRT is not directly connected with the downtown of Busan, the number of passengers won't increase. Busan should have reflected on the result of A'REX, which is used only by 6.9% of the estimated number of passengers.
In Japan, airport buses aren't forced to compete with railways, because most of the airport railways in Japan are extension or branch of conventional railway lines. In other words, if an airport railway line can't get enough passengers, it wouldn't affect the railway lines totally.
But in Korea, this is not the case. So, the authorities have to think seriously about management of airport railway lines.