Gimpo Airport runs two very different domestic routes. Jeju has no train at all, so the only question is what the ticket costs once a suitcase is added to it. Busan has the KTX running from the middle of Seoul to the middle of the city, so the real question is whether flying is worth it at all. This guide covers only Gimpo–Jeju and Gimpo–Gimhae, Busan’s airport — not Gimhae–Jeju, and not flights arriving from abroad.
Jeju: what the ticket actually costs
Every fare below is what one adult paid for a one-way economy seat on Wednesday 30 September 2026, checked 12 September 2026 — a booking-engine price for that date, not a published tariff, and it will move.
| Carrier | Fare on this date | Checked bag included |
|---|---|---|
| Jeju Air STANDARD (스탠다드) | ₩30,900 | 15 kg |
| Asiana discounted economy fare (특가운임) | ₩38,900 | 20 kg |
Both figures are stated by the carrier as an all-in total: airport fee and fuel surcharge already inside the price, nothing added at the counter. That makes this the one clean comparison in the whole topic, and the result runs against the obvious guess. Asiana’s ₩38,900, with 20 kg in the hold, undercut every low-cost carrier’s own published weekday tariff — September-2026-ticketing prices, ₩89,800 to ₩96,900 across the four of them — and sat only ₩8,000 above the cheapest low-cost seat on this date, which carries 5 kg less. On this date, “budget airline plus a bag” wasn’t actually the cheaper plan.
Korean Air also had seats on sale, but its results page prints no breakdown at all — no surcharge line, no note about what’s included — so there’s no way to tell whether its total is built the same way as the two above. That gap is why this guide doesn’t put a Korean Air figure next to Asiana’s: they aren’t measured the same way, and putting them side by side would imply they are.
What a suitcase costs beyond the free allowance isn’t published for either Jeju Air or Trinity Airways — more on that name below — because the price on both sites sits behind a calculator that wouldn’t return a number during this check. Where a bag price is published, it’s minor next to the fare: ₩8,000 for 5 kg booked in advance on Jin Air, ₩10,000 for 5 kg at Air Busan’s Jeju-route excess rate.
One more trap sits inside Korean Air’s own booking page: some of the cheapest fares listed under Korean Air’s KE flight numbers to Jeju are actually operated by Jin Air, as a codeshare. Their fare cards don’t print the usual 20 kg allowance — they say it’s only shown once you reach the payment page. If a “Korean Air” fare to Jeju looks unusually good, check who’s actually flying it before you count on 20 kg of luggage.
None of this is fixed. Jeju Air’s own fare calendar showed the same route swinging from ₩26,700 on the cheapest day to ₩131,400 on the most expensive, inside a single fortnight — a wider range than anything separating the carriers above. The date you fly moves the price more than the airline does.
Busan: the comparison that doesn’t close
Flying to Busan lands at Gimhae, on the edge of the city; the KTX runs into Busan Station instead. Before comparing them at all, it’s worth being honest about what’s actually measured.
| Leg | What’s published |
|---|---|
| Seoul Station → Gimpo | ₩1,750 by transit card on AREX’s All-Stop train — no journey time is published for this specific pair |
| Time needed at Gimpo | Check-in closes 30 minutes before departure on every carrier flying this route; the carriers themselves recommend arriving 40 to 50 minutes ahead |
| The flight | A 1h 05m scheduled block on most departures. Cheapest fare on this date: ₩57,800 (Jeju Air). Korean Air’s only remaining fare ran to ₩100,900 — its two cheaper buckets were already sold out, 18 days before the date |
| Gimhae → Busan Station | No published fare or journey time, on any of the fifteen transport modes the airport itself lists |
Add up the air side alone and a Gimpo-to-Gimhae trip runs roughly 1h 35m to 1h 55m from arriving at Gimpo to landing at Gimhae — the 1h 05m flight plus 30 to 50 minutes at the airport — for somewhere between ₩59,550 (this date’s cheapest fare plus the AREX ride) and ₩102,650 on the day’s pricier remaining fare. Neither total includes the two legs that actually decide the comparison.
Those two legs are the finding here, not a footnote. No operator publishes how long it takes to get from Seoul Station to Gimpo’s domestic terminal — AREX prices the ride but only times it as far as Incheon. And nothing publishes a fare or a journey time from Gimhae to Busan Station at all: the airport itself lists fifteen ways to leave the terminal, and Busan Station isn’t the endpoint of any of them. The best rail option is light rail into a transfer at Sasang onto the metro, and even that combined hop has no published price. Korea’s rail and bus fares for this exact corridor were checked separately, on 4 September 2026 — see KTX vs express bus — but a train fare in hand still wouldn’t finish this comparison, because it’s the flight’s own ground connections that are missing, not the train’s numbers.
So the honest answer is structural, not numeric: the flight itself is fast, the airport adds a fixed 30 to 50 minutes, and the two connections on either end are unmeasured by anyone who publishes a schedule. Whoever actually knows how long those two rides take is the only person who can finish this comparison — it can’t be completed from what airlines and the airport publish.
On Wednesday 30 September 2026, 17 flights left Gimpo for Gimhae — Korean Air’s first at 07:00, Air Busan’s last at 20:00 — but that’s a single day’s count on a schedule that runs only through 24 October 2026, not a year-round frequency. Jeju’s own service is a different shape entirely: more than a hundred departures a day, roughly every five to fifteen minutes from early morning to early evening, dense enough that timing rarely matters on that route.
Getting through Gimpo
One rule matters more than any fare here: your boarding pass has to match your passport, in the same script. Asiana states plainly that a name mismatch between your ticket and your ID stops you at check-in and again at the security screening area. Book in the exact Latin spelling on your passport, every time — this is the single most useful sentence in this guide for a visitor booking from abroad.
Gimpo’s own domestic-departure pages disagree on where the ID check actually happens. The Korean page places it at the entrance to the departure area, before security, with a guard checking your face against your ID — hat, mask and sunglasses off. The English page instead describes the check happening at the boarding gate. Plan for the earlier, stricter version and have your passport and boarding pass ready before security; that’s the safer reading of the two, and the one an English-speaking visitor doesn’t otherwise see.
Don’t plan on the biometric fast lane either. One of the airport operator’s own pages restricts it to Korean nationals; another lists a passport among the documents accepted at the registration desk. Neither page settles whether a foreign visitor can actually register, so treat the ordinary ID check as the plan rather than the shortcut.
An expired passport or a photocopy can’t be used to board a domestic flight, in terms, since 2022. And from 20 April 2026, passengers are limited to two power banks each, rated 160Wh or under — charging one, or using it to charge anything else, is banned outright once you’re on board.
Two carriers mid-rename, two mid-merger
T’way Air’s website now redirects everywhere to Trinity Airways — same operator, new name on every page, including the fare table quoted above. If you booked as T’way, or you’re searching for it, look for Trinity instead.
Korean Air and Asiana are due to merge into one integrated carrier on 17 December 2026. As of this check, neither airline’s booking flow mentions the other, and each still sells its own fares under its own flight numbers. A booking made now is a booking with the airline shown on the page — but if your travel date sits close to or past the merger date, confirm which brand’s baggage and change rules actually apply before relying on anything above.
What isn’t published
Whether the standard cabin-liquid limit even applies to a domestic flight isn’t clearly published by Korea’s aviation-security authority — pack as if it does until you can confirm otherwise. And the exact cost of extra baggage on Jeju Air and Trinity Airways is missing entirely, because both airlines route the price through a calculator that wouldn’t return a number during this check. If your fare’s free allowance is tight, get the figure from the airline’s own booking flow before you fly rather than from an estimate here.
What to actually book
For Jeju, compare the all-in total your own booking screen shows, not the headline fare — on this date, the full-service carrier with the bigger bag beat every low-cost option outright, and that can flip on a different day, so check the total again close to when you fly. For Busan, book the flight if the KTX doesn’t suit your schedule or your route into Seoul Station is awkward, but don’t expect flying to be measurably faster door to door: nobody publishes the two numbers that would prove it either way, in either direction.