Over the summer, the early JFK-LHR flight was the XP as was the late LHR-JFK flight. While I'm not sure, I believe the XP came into JFK at 3PM from NRT and then continued on to LHR. Similarly, I think the XP arrived JFK from LHR around 9PM and then continued to NRT the next day at 11AM. Unfortunately, now there is only one JFK-LHR flight, and I am not sure which equipment is used.