Virgin is promoting an official sale on daily flights during January 9 through March 31, 2019, from many of its American gateways onward to London. But when ticketing these fares, prices drop further below what they are advertising. When searching for these fares, you will notice that the prices on these itineraries fall dramatically on the final booking screen and cost even less when booking on the Delta website. As an example, I've provided a screenshot below. It's like a sale on top of another sale!
The hitch is, all fares book into Virgin and Delta's corresponding Light or Basic Economy fare buckets, meaning you'll only be allowed standard sized carry on baggage. Checked baggage will cost an additional $60 each way, which will significantly increase the price. Do keep in mind these are both full-service airlines, so meals, in-flight entertainment, and drinks will still be included. As opposed to flying on Norwegian who charge extra for those amenities and also serve many of these routes at a similar price point.
This sale is set to expire tomorrow at midnight October 3, 2018, so it's best to book before then as these fares might jump in price, given the unadvertised element of these fares. Delta allows a 24-hour cancellation grace period if you book a trip and change your mind overnight.
Nonstop sale fares include: