Portland PDX to London LGW and LHR tickets are on sale with all three alliances for about $487 to $556 round trip for travel in April and May 2017. Google Flights shows low fare dates with two-stop itineraries priced lowest. While Seattle to London Gatwick LGW is as low as $410 round trip with Icelandair, the major alliance airlines have tickets from Portland, Oregon PDX to both London Heathrow LHR and London Gatwick LGW with best deals found through online travel agency searches on Momondo.com or Skyscanner.com.
Momondo.com pulled up this TravelMerry.com $487 fare with Lufthansa and Air Canada.
Portland PDX – Vancouver YVR – London Heathrow LHR – Frankfurt FRA – Vancouver YVR – Portland PDX
$486.76 round trip Fri April 7 – Sat April 15
American Airlines/British Airways
Portland PDX – Phoenix PHX – New York JFK – London Gatwick LGW – New York JFK – Phoenix PHX – Portland PDX