AirHint found the following cheapest return flights from Seattle (SEA) to Porto (OPO) in May 2026 (see full year).
Return flights
| 17 May - 24 May | Air France | ||
| 20 May - 27 May | British Airways | ||
| 18 May - 25 May | British Airways | ||
| 21 May - 28 May | Delta | ||
| 19 May - 26 May | Delta | ||
| 22 May - 29 May | Delta |
Also check the deals for one-way flights from Seattle to Porto in May.
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