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

Return flights

26 Sep - 01 Oct	Luxair
29 Sep - 02 Oct	KLM
28 Sep - 02 Oct	KLM
29 Sep - 14 Oct	KLM
19 Sep - 25 Sep	Luxair
30 Sep - 07 Oct	Luxair
30 Sep - 02 Oct	SWISS
16 Sep - 19 Sep	KLM
26 Sep - 30 Sep	Luxair
29 Sep - 30 Sep	KLM
16 Sep - 23 Sep	KLM
23 Sep - 25 Sep	Lufthansa
29 Sep - 03 Oct	Luxair
29 Sep - 06 Oct	Luxair
30 Sep - 03 Oct	Luxair
16 Sep - 18 Sep	SWISS
16 Sep - 20 Sep	KLM
27 Sep - 07 Oct	Luxair
14 Sep - 23 Sep	KLM
23 Sep - 26 Sep	SWISS

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 288€

Return flights