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

One-Way flights

05 Sep	Philippine Airlines
21 Sep	Singapore Airlines	direct
19 Sep	Singapore Airlines	direct
04 Sep	Asiana Airlines
15 Sep	Asiana Airlines
16 Sep	Air Canada
13 Sep	Asiana Airlines
23 Sep	Air Canada
07 Sep	Air Canada
17 Sep	United

Also check the deals for return flights from Seattle to Singapore 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.

Book a cheap hotel in Singapore

Cheap car rent in Singapore

Cheapest one-way flights from Seattle to Singapore in September from 285€

One-Way flights