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

Return flights

05 May - 12 May	Air Canada
06 May - 13 May	Air Canada
13 May - 20 May	Air Canada
12 May - 19 May	Air Canada
11 May - 18 May	Air Canada
04 May - 11 May	Air Canada
07 May - 14 May	Air Canada
19 May - 26 May	Aer Lingus
15 May - 22 May	Air Canada
17 May - 24 May	Air Canada
26 May - 02 Jun	Aer Lingus
27 May - 03 Jun	Turkish Airlines
30 May - 06 Jun	WestJet
25 May - 01 Jun	Air Canada
24 May - 08 Jun	Lufthansa
28 May - 04 Jun	WestJet
29 May - 05 Jun	WestJet
31 May - 07 Jun	WestJet
29 May - 12 Jun	Air Canada

Also check the deals for one-way flights from Seattle 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 Seattle to Lisbon in May from 516€

Return flights