According to this below article, from the 2nd September for around a week the STN-JFK flights were to be operated by their older 737-800's and were operating via Keflavik for refuelling.
www.independent.co.uk/travel/news-and-advice/primera-air-london-stansted-nonstop-flights-new-york-refuel-iceland-reykjavik-a8509536.html
Did this end up happening?
Things seem a bit of a mess at Primera and I don't get this operating such small sub-fleets of different aircraft to operate the transatlantic routes.
Surely you would either operate a fleet of 737max or A321neo's to fly the routes and not a mix of both. For such a small airline the costs to operate a mixed fleet must be astronomical?!
I appreciate they have the older 737-800s to operate within Europe, but the long haul fleet with A321neos and LRs, plus more 737 Max's just seems a mess.