Originally Posted by
anabolism
xONEx seats are restricted, not just as much as, say, award seats. But as flights fill up, you're more likely to see fewer seats in A than F, fewer in D than J, and fewer in L than Y.
If you have an
ExpertFlyer premium subscription, you can set an alert for when your desired class (i.e., A, D, L) goes below some value (e.g., 5) and jump to book then.
(BTW, I have no idea if 5 would be a good threshold for use here. Maybe 7 or 3 would be better? But 5 seems plausible.)
Generally A and D are very easy to find as long as you plan at least a couple of months out, though of course not as abundant as F and J. The issues with availability in the premium cabins come more frequently when you need to make a last minute to change. L, on the other hand, is a comparatively much more difficult inventory to find.