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

Return flights

08 Sep - 04 Oct	Lufthansa
04 Sep - 11 Sep	Air Canada
27 Sep - 04 Oct	Lufthansa
26 Sep - 02 Oct	WestJet
17 Sep - 11 Oct	Air Canada
22 Sep - 18 Oct	Air Canada
30 Sep - 25 Oct	Air Canada
24 Sep - 18 Oct	Air Canada
25 Sep - 18 Oct	Air Canada
29 Sep - 25 Oct	Air Canada
11 Sep - 04 Oct	Air Canada
10 Sep - 17 Sep	WestJet
18 Sep - 22 Sep	Air Canada
11 Sep - 15 Sep	Air Canada
15 Sep - 29 Sep	Lufthansa
10 Sep - 17 Sep	Lufthansa	direct
05 Sep - 12 Sep	Air Canada
06 Sep - 13 Sep	Air Canada
04 Sep - 27 Sep	Air Canada
07 Sep - 27 Sep	Air France

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 615€

Return flights