So, let me get this right. The principle of the test is to see if someone is above a level of fitness in relation to their potential max ability in the areas that are tested (running, press-ups and sit-ups). This principle is confirmed by the existance of varying acceptable levels of achievement, depending on age and sex. It is not job-related, so it has no relevance to what we each do in our daily lives. Due to the foregoing facts, it is not sex-discriminatory, either.
Given all the above, which summarises most messages here, it has to be illegal for any employer (incl the RAF) to use it as a personnel management tool, methinks. This is despite the fact that it is desirable to keep fit. Encouragement is one thing, testing is another. Maybe this is why no-one, yet, has been discharged solely faling to come up to the mark, even after continuous remedial traing, etc.