As a note to those planning a DONE/AONE, you can purchase
extra segments in NA in either F/J or Y. However, if you save
the money and buy in Y, they book into full-Y and thus on AA
you get upgraded to F/J for free upon request, given that you are Elite.

Therefore, paying extra for the F/J segments is probably not worth
it, as you can choose which NA segments to book in Y,
based on the ability to upgrade.