I am not sure if it is a regulation thing, but I when I applied I was told that if I didn't get accepted to expect to wait 6 months. The reasoning being told to me was to increase my grades, ASTB scores, and get more flight hours to help pad the application. Not sure if their is an official policy, but it would seem the wait would help you in putting together a better package that might be more competitive, basically a period to improve yourself.