I would imagine that the 2 AAC SNCOs qualified for Late Entry Commissions, and that you possibly don't meet the criteria because of either age or length of service. The other thing to remember is that a number of AAC SNCOs started life in another cap-badge and that it isn't remarkably uncommon to meet a Sgt pilot who has already done Senior Brecon or an equivalent non-inf cadre. This type of experience would count for a lot when considering a LE commission that might not be gained as Airman Aircrew, which while grounding you on the professional aspects of the job might not tick all of the boxes in the RAF's criteria. A lot will probably also depend on the demand for officer's in your branch. If the RAF has a shortage of rotary pilots, AAC SNCOs will find it a lot easier to make the jump to RAF Officer than perhaps an RAF SNCO in a well recruited branch.