AirHint found the following cheapest return flights from Seattle (SEA) to Sydney (SYD) in December 2025 (see full year).
Return flights
| 24 Dec - 28 Dec | United | ||
| 27 Dec - 11 Jan | United | ||
| 30 Dec - 06 Jan | Frontier Airlines | ||
| 26 Dec - 02 Jan | United | ||
| 17 Dec - 23 Dec | Alaska Airlines | ||
| 20 Dec - 31 Dec | Alaska Airlines | ||
| 20 Dec - 27 Dec | United |
Also check the deals for one-way flights from Seattle to Sydney in December.
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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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