Seattle to Seoul: Cheapest Months, Best Airlines, and the ICN Transit Play
SEA to ICN is one of the most fairly-priced long-hauls from the West Coast, if you know which months to book and which connection to avoid.
A nonstop from Seattle-Tacoma to Incheon runs about 10 hours 30 minutes westbound and rarely dips below $850 in economy round-trip, but shoulder-season round-trips have printed at $720 as recently as this past February. On the revenue-management desk we called SEA-ICN a "thin but loyal" route: steady demand, three competing SkyTeam carriers, and bucket inventory that loosens fast once the Korean summer rush ends. If you're flexible by two weeks, you can often save more than a full economy fare.
Who actually flies SEA to ICN nonstop
Three carriers own the direct market, and all three sit inside SkyTeam, which matters for mileage earning and upgrades.
- Delta Air Lines: daily on the A330-900neo, Delta One suites up front, Premium Select in the middle cabin.
- Korean Air: daily on the 777-300ER, occasionally the A380 during peak summer, Prestige business class.
- Asiana Airlines: still operating under its own brand through the Korean Air merger integration window, A350 on most rotations.
Alaska Airlines does not fly this route nonstop. If you're paying in Mileage Plan miles, you'll route through LAX or SFO on a partner and eat an extra four hours, so it's rarely the right trade.
How a third carrier changes the price
Two-carrier routes let airlines hold fare floors. Three carriers don't. SEA-ICN has three competitors plus one-stop options on ANA via Narita and JAL via Haneda, which keeps the published economy floor lower than what you see on most flights to Asia from other US gateways where a single carrier effectively sets the premium floor.
Cheapest months to fly SEA to ICN
This is the table I'd tape to your monitor. Figures are approximate round-trip economy ranges I've tracked on this route over the last 12 months; premium cabin multipliers in the right column are what I've generally seen on Delta and Korean at the same booking windows.
| Month | Economy range (RT) | Premium Select / Prestige multiplier | Notes |
|---|---|---|---|
| January | $720-$900 | 3.2x | Post-holiday dead zone, best prices of the year |
| February | $740-$950 | 3.3x | Lunar New Year spike last week, book around it |
| March | $850-$1,050 | 3.4x | Cherry-blossom halo demand starts late March |
| April | $950-$1,200 | 3.5x | Peak photography traffic, tight premium inventory |
| May | $1,000-$1,250 | 3.6x | Korean Buddha's Birthday bump mid-month |
| June | $1,150-$1,450 | 3.8x | Summer pricing kicks in hard |
| July | $1,250-$1,600 | 4.0x | Worst month, Korean domestic summer travel overlaps |
| August | $1,200-$1,500 | 3.9x | Liberation Day (Aug 15) adds demand |
| September | $900-$1,100 | 3.4x | Chuseok week spikes, but shoulders are cheap |
| October | $830-$1,050 | 3.3x | Sweet spot for weather plus price |
| November | $800-$1,000 | 3.2x | Thanksgiving week aside, very reasonable |
| December | $950-$1,400 | 3.7x | Christmas/New Year peak, two-tier pricing |
Translation: if you can fly late October through mid-February with a Chuseok and a Lunar New Year carve-out, you're booking in the bottom third of the year. If your company is paying and your dates are locked, just book 45 to 90 days out and don't try to game it.
What about connecting through Japan
Two one-stop options are worth knowing because they occasionally undercut the nonstop by $200 or more.
- ANA via Narita (NRT): SEA-NRT on the 787-9, NRT-ICN on the shorter 737. Total travel time lands around 14 hours. On nonstop flights you save four hours, so only take the connection if the savings clear $250 or if you were going to break the trip in Tokyo anyway.
- JAL via Haneda (HND): better airport than Narita, but the same math applies.
I'd skip any itinerary that routes you via LAX or SFO. You're flying away from Asia to fly back, and the savings rarely justify the 18-hour total.
Premium cabin value on SEA-ICN
Korean Air's Prestige business class on the 777-300ER is the quiet win here. It's not Delta One Suites, but the seat is fully flat, the crew ratio is generous, and the cash price hovers 10 to 15 percent below Delta for the same dates. If you're paying with miles, Korean's SKYPASS charges 62,500 miles each way in Prestige, and SkyTeam partners can sometimes book it using Virgin Atlantic Flying Club miles at a discount when award space opens.
For a deeper comparison of what you're actually buying in business class flights across the major trans-Pacific carriers, the biggest differentiators this year are dining and Wi-Fi consistency, not the seat itself. Most widebodies on this route now have flat beds in J; the gap is in service.
Korean's own fare rules are published at koreanair.com, which is worth checking before you book a partner award, because the fuel-surcharge pass-through varies by booking carrier.
The K-ETA, the airport, and the part nobody tells you
US passport holders don't need a visa for short stays, but you do need a K-ETA. It runs $10, takes up to 72 hours to approve, and is technically waived for US passport holders through late 2026, though the Korean Immigration Service has been inconsistent about enforcement. Check the current status with the US State Department Korea page in the week before you fly.
Incheon itself is a world-class airport for transits. If you're continuing to Southeast Asia on Korean Air, the same-terminal connection is clean and the lounges are genuinely good. Book with a minimum connection time of 90 minutes and you'll be fine; 60 minutes is cutting it close if you need to re-clear security for a gate change.
How to actually book the cheapest fare
A few practical moves from the consolidator desk:
- Price the full round-trip on one PNR. Two one-ways on Delta and Korean will almost always cost more than the round-trip, because each direction gets its own fare bucket assignment.
- Search SEA-ICN AND PDX-ICN on the same dates. Portland doesn't have a nonstop, but the connecting price sometimes undercuts SEA by $150, and the positioning flight from PDX to SEA is cheap on Alaska.
- Check Tuesday and Wednesday departures. Saturday returns are the single worst pricing slot on this route.
- If you're a SkyMiles Medallion, the Delta A330-900 is the only way to get a confirmed Premium Select upgrade clear on this city pair.
Call our booking team for a quote that beats the public search, request a callback and we'll call you back within 30 minutes.
Frequently asked questions
What's the cheapest month to fly SEA to ICN?
January is consistently the lowest, with economy round-trips in the $720 to $900 range outside of Lunar New Year week. Late October and early November are a close second if the weather matters to you.
How long is the SEA to Seoul flight nonstop?
About 10 hours 30 minutes westbound and 9 hours 15 minutes eastbound. Jet stream tailwinds shave the eastbound return; that's not marketing, it's physics.
Is Delta or Korean Air better on this route?
Delta's A330-900neo has the better hard product in business with the Delta One Suite; Korean's 777-300ER has better food and a larger crew ratio. In economy they're comparable, and Korean's Prestige cash price is usually 10 to 15 percent cheaper.
Do I need a visa for South Korea from the US?
No visa for stays up to 90 days, but you'll typically need a K-ETA travel authorization. It's $10 and takes up to 72 hours to process. Confirm the current requirement with the US State Department before you book.
Are one-stop flights via Tokyo ever worth it?
Only if they save at least $250 over the nonstop or you were planning a Tokyo stopover anyway. Adding four hours of travel time for $100 of savings isn't a trade most travelers should make.