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

Return flights

30 Sep - 30 Oct	Icelandair
30 Sep - 16 Oct	Air Canada
30 Sep - 21 Oct	Aer Lingus
30 Sep - 13 Oct	Air Canada
29 Sep - 07 Oct	Air Canada
30 Sep - 07 Oct	Iberia
30 Sep - 07 Oct	Iberia	direct
30 Sep - 16 Oct	Finnair	direct
29 Sep - 07 Oct	United	direct
28 Sep - 26 Oct	Lufthansa
26 Sep - 29 Sep	SWISS
26 Sep - 30 Sep	SWISS
26 Sep - 30 Sep	United	direct
26 Sep - 28 Sep	United	direct
26 Sep - 29 Sep	United	direct
28 Sep - 30 Sep	Icelandair
28 Sep - 30 Sep	Finnair	direct

Also check the deals for one-way flights from Chicago 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 Chicago to London in September from $586

Return flights