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

Return flights

04 Sep - 24 Sep	WestJet
10 Sep - 18 Sep	Porter Airlines (Canada) Ltd
03 Sep - 12 Sep	Porter Airlines (Canada) Ltd
08 Sep - 20 Sep	Porter Airlines (Canada) Ltd
05 Sep - 15 Sep	Porter Airlines (Canada) Ltd
03 Sep - 11 Sep	Porter Airlines (Canada) Ltd
27 Sep - 10 Oct	Aer Lingus
27 Sep - 11 Oct	Aer Lingus
24 Sep - 02 Oct	Aer Lingus
04 Sep - 13 Sep	Air Canada
09 Sep - 26 Sep	Air Canada
10 Sep - 27 Sep	Lufthansa
09 Sep - 24 Sep	Lufthansa

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 $497

Return flights