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

Return flights

22 Sep - 02 Oct	Finnair
10 Sep - 18 Sep	Cathay Pacific
23 Sep - 29 Sep	Cathay Pacific
08 Sep - 15 Sep	Cathay Pacific
23 Sep - 03 Oct	Finnair
25 Sep - 08 Oct	jetBlue
18 Sep - 03 Oct	Cathay Pacific
10 Sep - 25 Sep	United
24 Sep - 04 Oct	Hawaiian Airlines
24 Sep - 03 Oct	Hawaiian Airlines
25 Sep - 03 Oct	Hawaiian Airlines
26 Sep - 05 Oct	Alaska Airlines
26 Sep - 06 Oct	Alaska Airlines
26 Sep - 04 Oct	Alaska Airlines

Also check the deals for one-way flights from Washington 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.

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Cheapest return flights from Washington to Singapore in September from $1018

Return flights