I have seen many posings on how to earn/ generate ff miles. However, an even more important subject as to how to use or which airline has the lowest number of ff miles for a certain trip seems to get no postings.The difference is huge : one airline had a special for 0nly 17.5k miles to Latin A. when for the same trip an other airline wanted 100k ff miles----that almost a 6 times difference. Or, is there a site to address this?