AirHint found the following cheapest one-way flights from Seattle (SEA) to Keflavik (KEF) in September 2025 (see full year).
One-Way flights
| 30 Sep | WestJet | ||
| 10 Sep | Alaska Airlines | ||
| 01 Sep | WestJet | ||
| 01 Sep | Icelandair | direct | |
| 30 Sep | Icelandair | direct | |
| 10 Sep | Icelandair | direct |
Also check the deals for return flights from Seattle to Keflavik in September.
The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.
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