It has something to do with the Army outside the AAC, (as apparently there is some) not bothering to apply for selection, thinking it was beyond the mere squaddie or some twoddle. That has hopefully been rebalanced as there was an article in Soldier mag about it. The more NCO's the better, and the latest rumour is if you are a Cpl when you start training at wings you get your third as well. Not sure if this decesion has made it to the army board yet though...