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

Return flights

05 Sep - 14 Sep	SWISS
10 Sep - 15 Sep	SWISS
24 Sep - 30 Sep	SWISS
04 Sep - 09 Sep	Lufthansa
17 Sep - 21 Sep	Lufthansa
04 Sep - 22 Sep	Lufthansa
05 Sep - 15 Sep	SWISS
11 Sep - 22 Sep	Lufthansa
25 Sep - 30 Sep	Lufthansa
15 Sep - 21 Sep	Lufthansa
16 Sep - 09 Oct	SWISS
24 Sep - 14 Oct	SWISS
26 Sep - 04 Oct	SWISS
18 Sep - 16 Oct	SWISS
02 Sep - 01 Oct	KLM
29 Sep - 13 Oct	KLM
29 Sep - 15 Oct	KLM
30 Sep - 13 Oct	KLM
29 Sep - 23 Oct	KLM
25 Sep - 02 Oct	SWISS

Also check the deals for one-way flights from London to Boston 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 Boston in September from $519

Return flights