All of the low flash-sale prices are good for one-way tickets available on Norwegian Air's website, and these are for flights departing air traffic hubs in the United States in November, December, and January -- with a select few also available in September and October. Keep in mind that these are only good for departing flights; the return flights will largely not be part of a sale, but you'd still be saving money here nonetheless.
Also, while the deals are hot, be sure to read the fine print and come prepared for the fact that Norwegian Air is still a budget airline. It makes plenty of money on fees like excess baggage and other odds and ends you might not have to pay for on another airline. Just do your due diligence, as you always should, before dropping any large heaps of money on your trip to finally gaze upon Buckingham Palace.
CNN Money lined up this helpful rundown of the hottest deals available from Norwegian Air, but you better book fast. This sale won't last long.