You mean private jets full of gold that are actually legal (though probably evading taxes) as opposed to the illegality of all the rest?
Furthermore, there is no way a private jet full of gold would actually fly. It would be too heavy to succeed in taking off. Gold is extremely dense, almost as dense as lead. You could put gold in a private jet, but it wouldn't be "full of" gold; there'd have to be a substantial amount of unused space for the thing to fly.