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

Return flights

08 Dec - 14 Dec	Royal Air Maroc
10 Dec - 17 Dec	Royal Air Maroc
10 Dec - 16 Dec	Royal Air Maroc
09 Dec - 16 Dec	Finnair
15 Dec - 10 Jan	Icelandair
13 Dec - 20 Dec	Frontier Airlines
14 Dec - 20 Dec	Frontier Airlines
11 Dec - 18 Dec	Aer Lingus
12 Dec - 29 Dec	Frontier Airlines
24 Dec - 07 Jan	Allegiant Air
16 Dec - 24 Dec	Aer Lingus
20 Dec - 27 Dec	Frontier Airlines
29 Dec - 04 Jan	Lufthansa
30 Dec - 04 Jan	SWISS
30 Dec - 03 Jan	TAP
25 Dec - 03 Jan	Frontier Airlines
27 Dec - 04 Jan	Lufthansa
26 Dec - 03 Jan	Porter Airlines (Canada) Ltd
27 Dec - 01 Jan	Allegiant Air
26 Dec - 04 Jan	Frontier Airlines

Also check the deals for one-way flights from Washington to Lisbon in December.

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 December from 539€

Return flights