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

Return flights

22 Sep - 29 Sep	Luxair
23 Sep - 25 Sep	Luxair
02 Sep - 17 Sep	KLM
21 Sep - 25 Sep	KLM
26 Sep - 29 Sep	Luxair
27 Sep - 29 Sep	Luxair
19 Sep - 22 Sep	Luxair
20 Sep - 25 Sep	Luxair
30 Sep - 03 Oct	Luxair
20 Sep - 22 Sep	Luxair
18 Sep - 22 Sep	Luxair
23 Sep - 02 Oct	KLM
23 Sep - 07 Oct	KLM
27 Sep - 01 Oct	Luxair
26 Sep - 06 Oct	Luxair
25 Sep - 01 Oct	Luxair
27 Sep - 02 Oct	Luxair
26 Sep - 05 Oct	KLM
30 Sep - 05 Oct	KLM
25 Sep - 02 Oct	KLM

Also check the deals for one-way flights from London 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 London to Porto in September from $253

Return flights