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

Return flights

22 Sep - 14 Oct	Aer Lingus
28 Sep - 28 Oct	Lufthansa	direct
30 Sep - 21 Oct	Aer Lingus
28 Sep - 29 Oct	Icelandair
29 Sep - 03 Oct	Icelandair
28 Sep - 02 Oct	Icelandair
29 Sep - 08 Oct	Air Canada
30 Sep - 21 Oct	British Airways	direct
29 Sep - 08 Oct	British Airways	direct
29 Sep - 06 Oct	Air Canada
20 Sep - 29 Sep	Air Canada
24 Sep - 29 Sep	Iberia
19 Sep - 25 Sep	Air France
19 Sep - 23 Sep	Aer Lingus
19 Sep - 24 Sep	Aer Lingus
23 Sep - 28 Sep	Air Canada
24 Sep - 28 Sep	Air Canada
25 Sep - 29 Sep	Iberia
26 Sep - 29 Sep	Iberia
24 Sep - 30 Sep	United	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 406€

Return flights