To get an appointment you need a nomination. Each MOC can submit 10 names and the SA will pick 1 of the 10 that met their standards. If no one met their standard then all 10 names goes into the national pool for later consideration. However if you have the LOA, all you need to make sure is your name is one of the ten names submitted and you will get the appointment provided other factors like (DodMerb) have no issues. During the interview with MOC or Senator's board of selection committee, they asked my DS whether he has received the LOA which he has. As stated in the wording of the LOA, you will be appointed once you received a nomination. So you don't have to be the at the top of the slate and that makes it a whole lot easier. I don't know how that works but someone told me a couple of years ago the LOA candidate doesn't count towards the 10 available slots and that's why MOC and Senator's committee will asked whether you have one or not. Now how the LOA is given, that's is a mystery. Somehow the SA feels that candidate is a must have for their SA so in order to not lose them to other SA or most likely other name brand schools, the LOA is issued to them. Also knowing that the nomination selection committee's decision is sometime subjective so to help them out, the LOA is given to ask them to please include their name as one of the nominee. Please correct me if I'm wrong.