Based on service of Icelandair you may consider to book some interesting fares to Seattle in America with a stop-over in Iceland during winter season 2016/2017. Round-trip flights are now available already for £303 or €354 when departing from UK or Scandinavia. Look for flights departing from London, Manchester, Birmingham, Glasgow, Oslo or Stockholm. For still attractive fare you may also consider to depart from Paris or Copenhagen. All charges and fees and 2x23kg checked luggage are included in base fare. 
if interested in this deal you may find the cheapest flights to America with possible stop-over in Iceland when flying between 27th of October and 20th of December 2016 or 4th of January till end of March 2017. (Date of your outbound flight to USA). Latest date of your return flight has to be 1st of May 2017. Max stay 1 month after arrival at turnaround. Icelandair offer free (up to 177h) stop-over in Iceland. More details here. The easiest way to check your connection possibilities is through Skyscanner. This tool gives you quickly a rough idea which low-cost airlines are connecting your home town.
Booking samples
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Booking sample of cheap flights to USA (Seattle) + Iceland from Europe at once from £303/€354 here. In this case you would be flying from Manchester to Reykjavik on 18th of November 2016. You would then move from Iceland to Seattle on 24th of November. Finally your return flight from America back to UK would be on 2nd of December 2016.
