AirHint found the following cheapest return flights from Singapore (SIN) to Seattle (SEA) in September 2025 (see full year).

Return flights

12 Sep - 14 Sep	United
12 Sep - 21 Sep	United
09 Sep - 16 Sep	United
11 Sep - 14 Sep	United
11 Sep - 13 Sep	United
18 Sep - 30 Sep	United
18 Sep - 23 Sep	United
23 Sep - 30 Sep	United
12 Sep - 20 Sep	United
27 Sep - 05 Oct	Air Canada
28 Sep - 05 Oct	Air Canada
22 Sep - 04 Oct	United
28 Sep - 06 Oct	United
09 Sep - 12 Sep	STARLUX Airlines
27 Sep - 05 Oct	Singapore Airlines	direct
28 Sep - 02 Oct	Singapore Airlines	direct

Also check the deals for one-way flights from Singapore to Seattle 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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Cheapest return flights from Singapore to Seattle in September from $788

Return flights