Anywhere in the UK to JFK would be a bit too long for an FR 738. STN's 3,400 mi, PIK's 3,200. The 738 reaches to just under 3,600 with 186 passangers.
Even moving outside the UK & closer to the US, SNN is still a gnats over 3,000 mi. Shortest single jump would be from NOC again just over 3,000.
JAS