Beckles,
Do you mean you are a Platinum Amex member? If so unfort. a person is not always gaurenteed avail. of cars. It is true that in some cases it may help out but there are a few times to where they will not be able to get anything at all.
As for what it takes to become a Centurion member I would kind if be interested in knowing as well. Not because I would want to be one but just to have a little incite for other people who may have that same question later on down the road.