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

Return flights

30 Sep - 14 Oct	Air Canada
23 Sep - 03 Oct	Air Canada
23 Sep - 30 Sep	Air Canada
22 Sep - 14 Oct	Air Canada
24 Sep - 14 Oct	Air Canada
29 Sep - 09 Oct	Air Canada
24 Sep - 30 Sep	Air Canada
22 Sep - 30 Sep	Virgin Atlantic
30 Sep - 07 Oct	Virgin Atlantic
30 Sep - 28 Oct	Finnair
29 Sep - 29 Oct	Finnair
30 Sep - 25 Oct	Air Canada
29 Sep - 06 Oct	Air Canada
19 Sep - 22 Sep	jetBlue
19 Sep - 27 Sep	jetBlue
20 Sep - 27 Sep	jetBlue
19 Sep - 23 Sep	jetBlue
24 Sep - 27 Sep	jetBlue
22 Sep - 27 Sep	jetBlue
22 Sep - 29 Sep	Air Canada

Also check the deals for one-way flights from Washington 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 Washington to London in September from $580

Return flights