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

Return flights

25 Sep - 09 Oct	Air Canada
18 Sep - 25 Sep	Air Canada
18 Sep - 29 Sep	Air Canada
18 Sep - 30 Sep	Air Canada
18 Sep - 14 Oct	Air Canada
13 Sep - 21 Sep	STARLUX Airlines
13 Sep - 20 Sep	STARLUX Airlines
07 Sep - 12 Sep	STARLUX Airlines
18 Sep - 28 Sep	Air Canada
18 Sep - 24 Sep	United
19 Sep - 25 Sep	United
18 Sep - 23 Sep	United
24 Sep - 01 Oct	Singapore Airlines

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 $675

Return flights