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

Return flights

27 Sep - 07 Oct	Air Canada
30 Sep - 06 Oct	Air Canada
27 Sep - 06 Oct	Air Canada
24 Sep - 07 Oct	Air Canada
24 Sep - 06 Oct	Air Canada
29 Sep - 06 Oct	Air Canada
29 Sep - 15 Oct	Air Canada
29 Sep - 07 Oct	Air Canada
09 Sep - 16 Sep	Air Canada
09 Sep - 09 Oct	Air Canada
21 Sep - 02 Oct	Air Canada
10 Sep - 16 Sep	Virgin Atlantic
10 Sep - 24 Sep	Delta
17 Sep - 22 Sep	Air Canada
23 Sep - 30 Sep	Delta	direct
21 Sep - 30 Sep	British Airways	direct
16 Sep - 23 Sep	Air Canada
09 Sep - 16 Sep	Delta	direct
10 Sep - 16 Sep	Delta	direct
20 Sep - 30 Sep	Air Canada

Also check the deals for one-way flights from San Francisco to London 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 San Francisco to London in September from $546

Return flights