There is a procedure for throwing people out who continuously failing the fitness test. The procedure is very fair and gives individuals every chance to get fit and save their jobs. From memory, I think it would take around 18 months from first failing the test to being thrown out if given all the chances dictated in the guidlines. So, for 18 months you have an admin burden and some one who can not deploy. However, continuous cock-up in the paperwork and Flt Cmdrs not following the guidlines usual mean people get away with it anyway.