American Airlines with Oneworld partner Finnair has ticket prices down to $447 for travel in August and $387 round trip Los Angeles to Stockholm or Gothenburg, Sweden for travel April/May and October to Feb 2018.
Star Alliance has similar ticket prices and Delta/SkyTeam are about $20 to $30 more.
American Airlines Los Angeles LAX – New York JFK – Helsinki HEL – Stockholm Bromma BMA – Helsinki HEL – JFK – LAX
Lufthansa Airlines ticket for Swiss Airlines flights
Los Angeles LAX – Zurich ZRH – Stockholm ARN – Zurich ZRH – LAX
American Airlines Los Angeles LAX – Chicago ORD – Helsinki HEL – Gothenburg GOT – London LHR – LAX