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

Return flights

19 Sep - 28 Sep	Scandinavian Airlines
10 Sep - 15 Sep	Aer Lingus
24 Sep - 29 Sep	Aer Lingus
14 Sep - 21 Sep	Scandinavian Airlines
03 Sep - 11 Sep	Aer Lingus
17 Sep - 24 Sep	Aer Lingus
23 Sep - 29 Sep	Aer Lingus
22 Sep - 13 Oct	Aer Lingus
15 Sep - 22 Sep	Aer Lingus
17 Sep - 22 Sep	Aer Lingus
11 Sep - 18 Sep	SWISS
30 Sep - 07 Oct	SWISS
29 Sep - 07 Oct	SWISS
26 Sep - 01 Oct	SWISS
27 Sep - 14 Oct	Scandinavian Airlines
22 Sep - 06 Oct	Aer Lingus
27 Sep - 01 Oct	SWISS
27 Sep - 02 Oct	Austrian Airlines
28 Sep - 14 Oct	Austrian Airlines
09 Sep - 03 Oct	United

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 $434

Return flights