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

Return flights

27 Aug - 10 Sep	Air Canada
27 Aug - 01 Sep	Air Canada
18 Aug - 02 Sep	Aer Lingus
12 Aug - 26 Aug	Aer Lingus
20 Aug - 28 Aug	Aer Lingus
18 Aug - 26 Aug	Aer Lingus
11 Aug - 20 Aug	Aer Lingus
20 Aug - 25 Aug	Air Canada
06 Aug - 20 Aug	Aer Lingus
19 Aug - 26 Aug	Aer Lingus
10 Aug - 19 Aug	Aer Lingus
26 Aug - 04 Sep	Air Canada
25 Aug - 04 Sep	SWISS
05 Aug - 11 Aug	Air Canada
04 Aug - 13 Aug	Aer Lingus
25 Aug - 08 Sep	SWISS
18 Aug - 02 Sep	British Airways	direct
27 Aug - 02 Sep	British Airways	direct
07 Aug - 04 Sep	Aer Lingus
31 Aug - 11 Sep	Iberia

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 $473

Return flights