[4] IIARCo contracted project management and the supply of equipment and trains, altogether worth about €400 million, to Incheon Korean French Consortium (IKFC).

Phase 2 of the line runs from Gimpo International Airport to Seoul Station, which increased the length to 58 km (36 mi).

This section was built in a cut and cover tunnel running parallel to Susaek and Gajwa before connecting with Hongik University and Gongdeok, then diving to terminate deep underground on the west side of Seoul Station.

However, KTX service began to run from Yongsan Station to Incheon International Airport on June 30, 2014.

[18][19] On September 1, 2010, the South Korean government announced a strategic plan to reduce travel times from Seoul to 95% of the country to under 2 hours by 2020.

a proposal for Seoul Subway Line 9 to combine with the AREX line via a direct connection at the Gimpo International Airport Station starting in 2020, providing a through service from Incheon International Airport to the Gangnam area with a travel time of about one hour.

[22] AREX operates two types of trains, one for commuter and one for express services, both supplied by Hyundai Rotem.

[23] Both train types offer disabled seats and are equipped with LCD screens for passenger information,[23] including flight arrivals and departures.

Following the opening of the second phase, Seoul–Incheon International Airport travel time on half-hourly Express services is 43 minutes to Terminal 1.

[10] Express train passengers boarding certain airlines can check in to their flights at the Seoul Station City Airport Terminal on the western side of Seoul Station,[24] which include facilities to check in and x-ray baggage, receive exit stamps from an onsite Korean Immigration Service officer, and permit expedited security screening once at Incheon.

[26] The AREX line is shown on Seoul subway maps as sky blue, often bisected with orange striping.

AREX Express train stations and ticket windows are easily by their distinct orange color scheme.

AREX Express trains offer 2+2 configured reclining seating, ample luggage storage, free WiFi, onboard service attendants and electronic entertainment screens.

AREX Express passengers have access to connecting shuttle buses at Seoul Station to partner hotels, to a dedicated boarding lounge at Incheon Airport Terminal 1, and exclusive use of Seoul Station's City Airport Terminal when departing.

[33][34] In late March 2018, KTX service to and from the airport was suspended because of low ridership[35] and the suspension became permanent in September 2018 as the line was officially abolished.

[18][19] At the time of the 2018 Winter Olympics, the Korean Ministry of Land, Infrastructure and Transport reported at 15% demand on weekdays.

[10] By 2022, the fares for the full length of the AREX line settled on ₩4,750 for commuter trains,[39] and ₩9,500 for Express service[40] and both require an additional ₩500 deposit if traveling by a single use card.