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

Return flights

10 Sep - 21 Sep	SWISS
12 Sep - 20 Sep	SWISS
12 Sep - 14 Sep	Air Canada
11 Sep - 20 Sep	Lufthansa
10 Sep - 17 Sep	SWISS
04 Sep - 08 Sep	SWISS
09 Sep - 15 Sep	SWISS
09 Sep - 14 Sep	Lufthansa
03 Sep - 13 Sep	Lufthansa
10 Sep - 14 Sep	Lufthansa
17 Sep - 01 Oct	Air Canada
11 Sep - 19 Oct	Lufthansa
09 Sep - 04 Oct	Lufthansa
21 Sep - 12 Oct	Air Canada
09 Sep - 04 Oct	Air Canada	direct
21 Sep - 12 Oct	Lufthansa	direct
26 Sep - 04 Oct	British Airways	direct
23 Sep - 05 Oct	Delta
29 Sep - 11 Oct	Virgin Atlantic
29 Sep - 11 Oct	British Airways	direct

Also check the deals for one-way flights from London to Montreal 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 London to Montreal in September from $467

Return flights