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

Return flights

23 Aug - 30 Aug	Icelandair
25 Aug - 09 Sep	Icelandair
28 Aug - 17 Sep	Icelandair
26 Aug - 13 Sep	Air Canada
27 Aug - 03 Sep	United
14 Aug - 21 Aug	Frontier Airlines
25 Aug - 01 Sep	British Airways	direct
17 Aug - 24 Aug	United
15 Aug - 22 Aug	KLM
05 Aug - 12 Aug	United
06 Aug - 15 Aug	KLM
16 Aug - 20 Aug	Icelandair
07 Aug - 14 Aug	Icelandair
11 Aug - 18 Aug	United
01 Aug - 08 Aug	British Airways
28 Aug - 17 Sep	British Airways	direct
30 Aug - 06 Sep	British Airways

Also check the deals for one-way flights from Portland to London in August.

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 August from $612

Return flights