AirHint found the following cheapest return flights from Boston (BOS) to Porto (OPO) in September 2025 (see full year).

Return flights

02 Sep - 19 Sep	United
22 Sep - 30 Sep	SWISS
19 Sep - 10 Oct	Austrian Airlines
01 Sep - 08 Sep	TAP
29 Sep - 25 Oct	Iberia
20 Sep - 01 Oct	United
08 Sep - 14 Sep	Air Canada
27 Sep - 18 Oct	SWISS
19 Sep - 24 Sep	Austrian Airlines
02 Sep - 18 Sep	KLM
13 Sep - 29 Sep	SWISS
08 Sep - 14 Sep	TAP	direct
12 Sep - 04 Oct	Iberia
17 Sep - 22 Sep	British Airways
22 Sep - 27 Sep	British Airways
27 Sep - 18 Oct	TAP	direct

Also check the deals for one-way flights from Boston to Porto 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 Boston to Porto in September from 382€

Return flights