Icelandair has round-trip flights from Seattle (SEA) to Stockholm, Zurich, Rome, Paris, Munich, Manchester, Barcelona, Helsinki, or Amsterdam (ARN, ZRH, FCO, CDG, MUC, MAN, BCN, HEL, AMS) for $357-$397 with a connection. Most flights between October to February, but Rome is limited to December to January.
A Carry on bag (20-lbs @ 21.6 x 15.7 x 7.8 inches) and a personal item (15.7 x 11.8 x 5.9 inches) is allowed for free on Icelandair. You can avoid seat selection fees by accepting the randomly assigned seat at the gate.
Paris, Munich, Amsterdam, and Manchester are the most expensive fares in this group, about $433-$499, round-trip.
Some small OTAs on Skyscanner have this for cheaper than the airline. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.
Click for more details and booking links Cheap Flights: Seattle to Stockholm, Zurich, Rome, Paris, Munich, Manchester, Barcelona, Helsinki, or Amsterdam $357-$499 r/t [Oct-Feb / FCO: Dec-Jan] – Icelandair