AirHint found the following cheapest return flights from Washington (IAD) to Lisbon (LIS) in May 2026 (see full year).

Return flights

01 May - 14 May	Royal Air Maroc
17 May - 24 May	Aer Lingus
13 May - 23 May	Royal Air Maroc
19 May - 25 May	Iberia
21 May - 28 May	Porter Airlines (Canada) Ltd
18 May - 23 May	Scandinavian Airlines
01 May - 14 May	TAP	direct
25 May - 01 Jun	Royal Air Maroc
20 May - 30 May	Royal Air Maroc
24 May - 30 May	Royal Air Maroc
24 May - 01 Jun	Royal Air Maroc
16 May - 23 May	Icelandair
25 May - 10 Jun	Aer Lingus
24 May - 01 Jun	TAP	direct
27 May - 05 Jun	Royal Air Maroc
25 May - 10 Jun	TAP	direct
25 May - 01 Jun	TAP	direct
30 May - 06 Jun	TAP

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

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 May from 484€

Return flights