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

Return flights

23 Sep - 30 Sep	Delta
24 Sep - 02 Oct	Virgin Atlantic
16 Sep - 23 Sep	Delta
13 Sep - 04 Oct	KLM
25 Sep - 29 Sep	Delta
27 Sep - 04 Oct	Virgin Atlantic
10 Sep - 17 Sep	Delta
10 Sep - 24 Sep	Delta
14 Sep - 24 Sep	Virgin Atlantic
11 Sep - 18 Sep	Delta
08 Sep - 04 Oct	Virgin Atlantic
12 Sep - 23 Sep	Virgin Atlantic
30 Sep - 05 Oct	Delta
19 Sep - 22 Sep	Delta
29 Sep - 25 Oct	Virgin Atlantic
26 Sep - 29 Sep	Virgin Atlantic
20 Sep - 11 Oct	KLM
17 Sep - 11 Oct	Virgin Atlantic
29 Sep - 02 Oct	Frontier Airlines
19 Sep - 24 Oct	KLM

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.

Book a cheap hotel in London

Cheap car rent in London

Cheapest return flights from Chicago to London in September from 451€

Return flights