Frontier Airlines ICN Terminal (ICN) in Seoul, South Korea, is not served by Frontier Airlines. Frontier is a low-cost airline located in the United States that mostly flies to local and a few foreign locations in North and Central America. For flights between Incheon and Frontier's operating areas, passengers should look at other airlines. https://www.airportsbuddy.com/frontier-airlines/frontier-airlines-icn-terminal-incheon-international-airport/