What Gimpo Is For
Gimpo (GMP) is Seoul's original airport and today it's primarily a domestic hub — flights to Busan/Gimhae, Jeju, Daegu, Gwangju, Ulsan, Yeosu, Pohang-Gyeongju, Cheongju, Sacheon, Muan, Gunsan, Yangyang, and Wonju all run out of Gimpo, each with its own quick-switch link on the airport's own site (a sign of how much domestic traffic it handles).
Gimpo also keeps a separate international terminal, with its own dedicated parking (basement and parking-building lots distinct from the domestic lots) and its own check-in and cargo check-in areas — so the international role is real, not incidental. I was not able to confirm the current list of international destinations from Gimpo's official flight-schedule pages: the schedule page splits into domestic and international tabs, but the international tab's actual city list only loads interactively and didn't render in a fetchable form. If a specific international route into Gimpo matters for your trip, confirm directly with your airline or a live flight search rather than assuming a route exists.
Reaching Central Seoul — and How It Compares to Incheon
Gimpo's biggest practical advantage is distance. The airport confirms its own station connects to Seoul Subway Line 5, Line 9, and the Airport Railroad (AREX). For comparison: AREX itself quotes the trip from Incheon Airport Terminal 1 to Gimpo Airport at about 44 minutes, and from Incheon T1 all the way to Seoul Station at about 66 minutes — meaning Gimpo sits roughly two-thirds of the way from Incheon to central Seoul already. In practice, that makes Gimpo noticeably faster to reach from most of the city than Incheon is, especially if you're headed to western Seoul (Gimpo's own borough, Gangseo-gu) or anywhere on Lines 5 or 9.
Terminal Layout: Domestic vs. International
Domestic and international operations at Gimpo are treated as separate facilities rather than one shared building — the airport's own parking guide lists distinct domestic lots (Parking No. 1 and No. 2) and separate international lots (an underground lot and a parking building), and public-transit pickup points are also given separately by terminal (for example, buses load from a specific domestic-terminal door). I could not confirm the exact walking distance or whether a shuttle connects the two terminal buildings directly — check signage or ask staff on arrival if you need to move between them.
Facilities
Gimpo's international terminal has a valet parking service for international departures (drop off at the 2nd-floor Information Counter, pick up on the 1st floor; operated by Turu VALET+, 02-2660-2899). There's a paid waiting room (유료 대합실) with TV, internet-connected laptops, flight information displays, and coffee — one room on the 3rd floor general waiting area and one on the 1st floor arrival hall, priced at ₩55,000 for up to two hours domestic (₩11,000 each additional hour) or ₩77,000 international (₩22,000 each additional hour); book a day ahead by phone (02-2660-2402~3).
The domestic terminal has an outdoor observation deck on its 4th floor, and the airport notes the adjacent National Aviation Museum nearby as another aviation-themed stop — but I could not confirm the observation deck's operating hours or any admission fee from the official page.
Attached to the airport is Sky City, a large commercial complex connected directly to the terminal and open to the general public, not just travelers. It includes a Lotte Mall (department store, Lotte Cinema, Lotte City Hotel, Lotte Mart), a "Sky Park" green space described as open to "airport users and citizens alike," a spine/joint/pain-medicine hospital (Wooridul Hospital), and a 200-bay golf driving range.
How Early to Arrive for a Domestic Flight
Gimpo's site describes a biometric fast-check-in system (facial recognition and fingerprint) that streamlines the domestic check-in process, but I could not find a published general recommendation (e.g., "arrive two hours before departure") or a check-in cutoff time on the pages I could access. Treat your airline's own check-in deadline as the real number, and don't rely on this guide for a specific cutoff.
Transferring Between Gimpo and Incheon
If you're connecting between the two airports, the Airport Railroad (AREX) is the direct link: Gimpo Airport is a confirmed stop on the AREX line between Incheon Airport and Seoul Station, and Incheon quotes the Gimpo-to-Incheon-T1 leg at about 44 minutes. There is also a dedicated limousine bus, route 6707A, running from Gimpo's domestic terminal (door 14) directly to Incheon International Airport, costing ₩7,500, with a first departure at 03:55 and a last one at 21:30 — useful if you land at Gimpo very early and need to be at Incheon well before a morning international flight. Build in real buffer beyond the quoted transit time for security and check-in at the other end; neither source states a minimum recommended connection window between the two airports.
Parking and Taxis
Gimpo has four parking lots with a combined capacity of about 6,000 vehicles. Confirmed fee structure for small vehicles: ₩1,000 for the first 30 minutes, then ₩500 per additional 15 minutes, with a 24-hour flat rate of ₩20,000 on weekdays and ₩30,000 on weekends/holidays. Large vehicles run ₩1,200 for 30 minutes plus ₩400 per additional 10 minutes, with a ₩40,000 24-hour flat rate. Multi-day stays are charged on a per-day basis at these same daily rates. Taxi pickup at the domestic terminal is specifically routed through gates 6 and 8, according to the airport's own transit guide.
Who Should Choose Gimpo Over Incheon
Based purely on what's verifiable here: anyone flying domestically within Korea has no real choice — Gimpo is the Seoul domestic hub, full stop. For international travelers, Gimpo only makes sense if your specific route is one of the (unconfirmed, from this session's research) short-haul international flights it operates — and if so, the payoff is a meaningfully shorter ride into central Seoul than Incheon offers, given Gimpo's closer position on the same AREX line. If your international flight only serves Incheon, none of that matters — you'll be routed there regardless of preference.