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

Return flights

29 Sep - 08 Oct	Air Canada
29 Sep - 08 Oct	Lufthansa	direct
22 Sep - 02 Oct	Air Canada
25 Sep - 07 Oct	Air Canada
21 Sep - 11 Oct	Air Canada
30 Sep - 25 Oct	Lufthansa
22 Sep - 18 Oct	Air Canada
23 Sep - 18 Oct	Air Canada
20 Sep - 11 Oct	Air Canada
24 Sep - 18 Oct	Air Canada
20 Sep - 24 Sep	Air Canada
20 Sep - 27 Sep	Air Canada
19 Sep - 23 Sep	Air Canada
24 Sep - 26 Sep	Porter Airlines (Canada) Ltd
25 Sep - 27 Sep	Air France
23 Sep - 25 Sep	Porter Airlines (Canada) Ltd
22 Sep - 24 Sep	TAP
22 Sep - 29 Sep	Lufthansa	direct
20 Sep - 27 Sep	Air Canada	direct
20 Sep - 24 Sep	Air Canada	direct

Also check the deals for one-way flights from Ottawa 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 Ottawa to London in September from $651

Return flights