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

Return flights

30 Sep - 07 Oct	jetBlue
29 Sep - 06 Oct	Air Canada
22 Sep - 24 Sep	jetBlue
25 Sep - 03 Oct	Air Canada
30 Sep - 25 Oct	Iberia
15 Sep - 11 Oct	Air Canada
17 Sep - 23 Sep	Air Canada
30 Sep - 08 Oct	Iberia
24 Sep - 28 Sep	Air Canada
23 Sep - 27 Sep	jetBlue
13 Sep - 20 Sep	Air Canada
25 Sep - 28 Sep	Air Canada
19 Sep - 28 Sep	Scandinavian Airlines
18 Sep - 24 Sep	Air Canada
24 Sep - 01 Oct	Air Canada
19 Sep - 29 Sep	Scandinavian Airlines
20 Sep - 28 Sep	jetBlue
13 Sep - 04 Oct	Air Canada
24 Sep - 03 Oct	jetBlue
25 Sep - 01 Oct	Finnair

Also check the deals for one-way flights from Washington to Lisbon 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 Lisbon in September from $637

Return flights