One thing I'm quite confident on is the aircraft choice was not a factor in 99.999% of passenger bookings. Without starting yet another 757 TATL debate, the aircraft provided seats, with TVs and food attached to them and all of those seats went non stop Newcastle to New York. Nobody cares. A plane really is a plane particularly when we are talking a relatively short flight. I can imagine the amount of people who choose not to fly the route because it was a 757 could be counted on one hand. Anyway they best get used to narrow body TATL with the 321NEO and the 737MAX only going to make it more common.
A lot is made on here regarding the pricing. However I must say that the fares down the back were in line with expectations as to what should be charged for a peak time fare and the Atlantic.
Airlines have been charging more for one ways than they have for return flights for decades. It was only a year or so that KLM started offering discounted one ways. Before that a single was twice the price of a return fare. BA domestics were the same years ago.
It was a use it or loose it. Nobody used it and now NCL has lost it. I don't think the 787 or the new UA Polaris product would have saved it. Yes there were cheaper one stop alternatives but the direct flight factor should mean better yields were chargeable.