Incheon International Airport Railroad ( A ` REX ) and Incheon International Airport Highway were built to increase the accessibility to Seoul . The airport is operated by Incheon International Airport Corporation ( IIAC ) and it is owned by the government of South Korea . The Incheon International Airport Railroad connects Incheon International Airport to Gimpo International Airport and Seoul Subway Line 5 and Line 9 which opened March 23 , 2007 .