Originally Posted by
BA850
Confirmed for LH at Boston, but only to Gates E10 and E11. I’m not sure how often E11 is used, as it is often occupied by BA’s A380, so in practice lounge boarding seems to be mostly for Gate E10.
Gates E9 and E12 are also commonly used by Lufthansa - to which you’d have to walk.
I think Emirates or Etihad also has board from lounge option at JFK, or used to.