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

Return flights

24 Sep - 15 Oct	Icelandair
29 Sep - 06 Oct	Icelandair
27 Sep - 06 Oct	Icelandair
10 Sep - 24 Sep	Lufthansa
30 Sep - 07 Oct	United
24 Sep - 01 Oct	United
29 Sep - 08 Oct	United
01 Sep - 16 Sep	Icelandair
22 Sep - 26 Sep	Icelandair
09 Sep - 23 Sep	Air Canada
09 Sep - 19 Sep	United
10 Sep - 01 Oct	United
26 Sep - 06 Oct	Lufthansa
07 Sep - 15 Sep	Lufthansa
22 Sep - 29 Sep	Air Canada
19 Sep - 26 Sep	United
13 Sep - 03 Oct	United
14 Sep - 21 Sep	United
21 Sep - 11 Oct	Air Canada
12 Sep - 19 Sep	United

Also check the deals for one-way flights from Portland 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 Portland to London in September from 475€

Return flights