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

Return flights

30 Sep - 08 Oct	Iberia
29 Sep - 13 Oct	Iberia
24 Sep - 01 Oct	Iberia
23 Sep - 30 Sep	WestJet
15 Sep - 18 Sep	Scandinavian Airlines
28 Sep - 01 Oct	WestJet
27 Sep - 04 Oct	Iberia
12 Sep - 04 Oct	Scandinavian Airlines
27 Sep - 18 Oct	TAP
14 Sep - 19 Sep	TAP
14 Sep - 21 Sep	TAP
30 Sep - 14 Oct	British Airways
27 Sep - 11 Oct	TAP
13 Sep - 04 Oct	TAP
14 Sep - 17 Sep	WestJet
26 Sep - 28 Sep	British Airways
22 Sep - 23 Sep	British Airways
22 Sep - 26 Sep	British Airways
20 Sep - 26 Sep	British Airways
13 Sep - 27 Sep	British Airways

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 826€

Return flights