AirHint found the following cheapest return flights from Ontario (ONT) to Sydney (SYD) in September 2025 (see full year).

Return flights

22 Sep - 02 Oct	China Airlines
20 Sep - 15 Oct	China Airlines
23 Sep - 15 Oct	China Airlines
24 Sep - 15 Oct	China Airlines
22 Sep - 29 Sep	China Airlines
20 Sep - 28 Sep	China Airlines
22 Sep - 25 Sep	China Airlines
23 Sep - 26 Sep	China Airlines
30 Sep - 06 Oct	China Airlines
30 Sep - 02 Oct	China Airlines
18 Sep - 24 Sep	Qatar Airways
27 Sep - 12 Oct	China Airlines
20 Sep - 27 Sep	Etihad Airways

Also check the deals for one-way flights from Ontario to Sydney 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 Ontario to Sydney in September from $2188

Return flights