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

Return flights

09 Sep - 25 Sep	Aer Lingus
22 Sep - 29 Sep	WestJet
18 Sep - 22 Sep	WestJet
11 Sep - 21 Sep	WestJet
20 Sep - 27 Sep	WestJet
06 Sep - 27 Sep	WestJet
08 Sep - 22 Sep	WestJet
10 Sep - 24 Sep	WestJet
17 Sep - 22 Sep	WestJet
10 Sep - 20 Sep	WestJet
29 Sep - 08 Oct	Air Canada
22 Sep - 18 Oct	Air Canada
24 Sep - 09 Oct	Lufthansa	direct
23 Sep - 08 Oct	Air Canada
24 Sep - 09 Oct	Lufthansa
20 Sep - 11 Oct	Air Canada
29 Sep - 08 Oct	Lufthansa	direct
26 Sep - 18 Oct	Air Canada
08 Sep - 04 Oct	Air Canada
10 Sep - 04 Oct	Air Canada

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 $660

Return flights