Here is an April 2017 airfare deal with all three major alliances priced from $560 to $575 for Portland, Oregon PDX to London. This is a limited time frame sale only for departures from about April 6 to May 10, 2017.
United-Star Alliance has the earliest departure date at April 6. Delta-SkyTeam have the latest low fare departure date from PDX on May 10 at $574. American and British Airways dates fall between those.
British Airways Portland PDX – Seattle SEA – London LHR – San Francisco SFO – Portland PDX
$573.73 round trip BA Economy O Class
This itinerary earns 50 Tier Points in BA Executive Club and nearly 3,000 Avios points. Or earn about 2,500 RDM in AAdvantage and 5,000+ EQM.
United Airlines Portland PDX – Vancouver YVR – London LHR – San Francisco SFO – Portland PDX
$569.16 round trip in UA Economy K Class Tue May 2 – Wed May 10