AirHint found the following cheapest return flights from Washington (IAD) to London (LCY) in August 2025 (see full year).

Return flights

11 Aug - 20 Aug	KLM
18 Aug - 27 Aug	KLM
06 Aug - 20 Aug	KLM
19 Aug - 26 Aug	KLM
18 Aug - 28 Aug	KLM
13 Aug - 20 Aug	KLM
18 Aug - 26 Aug	KLM
12 Aug - 21 Aug	KLM
19 Aug - 29 Aug	KLM
11 Aug - 02 Sep	KLM
17 Aug - 10 Sep	KLM
18 Aug - 10 Sep	KLM
19 Aug - 10 Sep	KLM
20 Aug - 10 Sep	KLM
17 Aug - 26 Aug	KLM
31 Aug - 12 Sep	SWISS
31 Aug - 09 Sep	KLM
31 Aug - 11 Sep	KLM
22 Aug - 10 Sep	KLM
16 Aug - 10 Sep	SWISS

Also check the deals for one-way flights from Washington to London in August.

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 Washington to London in August from $565

Return flights