WOW Air is offering 50% off all flights booked TODAY only. This is for travel January 14 through April 5, 2017. You can check fares and book here.
To receive the discount, make sure to enter the promo code WOWXMAS16. Unfortunately, the 50% discount is only on the base price and not the taxes, which makes up about half the fare. Either way though, I am still seeing extremely inexpensive flights! On a quick search I saw fares for $200 roundtrip between Boston and Iceland.
WOW Air has flights between Boston, San Francisco, Los Angeles, Baltimore, New York (Newark), Miami, and Pittsburgh direct to Iceland. From there you can continue on to many European cities as well!
I personally flew WOW Air about a year and a half ago from Boston to Iceland and had a great experience. While there is no luxury, it is a quick and easy flight and beyond cheap so I didn’t care!