Originally Posted by Tokyoite

Are you looking for a one-way JFK-HKG, or a return? FYI, you of course cannot use the HKG lounges if your JAL flight terminates in HKG.
For a one way F-J, use the multi-city tool and input JFK-TYO in leg 1, then TYO-HKG in leg 2.
for a return, do the reverse for leg 3 and 4.
obviously you need to first check on BA or JAL websites on which dates actually have availability to begin with.

here is a result i found with a quick search.