AirHint found the following cheapest return flights from London (LHR) to San Francisco (SFO) in September 2025 (see full year).

Return flights

30 Sep - 17 Oct	SWISS
29 Sep - 05 Oct	SWISS
30 Sep - 07 Oct	Lufthansa
27 Sep - 28 Sep	Air Canada
27 Sep - 30 Sep	Air Canada
28 Sep - 16 Oct	Lufthansa
30 Sep - 14 Oct	Air Canada
30 Sep - 15 Oct	Air Canada
28 Sep - 11 Oct	SWISS
29 Sep - 13 Oct	Lufthansa
28 Sep - 05 Oct	SWISS
29 Sep - 16 Oct	Lufthansa
27 Sep - 29 Sep	Virgin Atlantic	direct
27 Sep - 28 Sep	Virgin Atlantic	direct
27 Sep - 30 Sep	Virgin Atlantic	direct
22 Sep - 28 Sep	SWISS
24 Sep - 28 Sep	SWISS
22 Sep - 29 Sep	SWISS
25 Sep - 28 Sep	SWISS
26 Sep - 29 Sep	Austrian Airlines

Also check the deals for one-way flights from London to San Francisco 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 San Francisco in September from 418€

Return flights