Based on what the deal Citi struck up with AMR last year on a very large advance payment portion of the miles stretching into 2005 or 2006, the lengthy thread in AA forum at that time speculated the cost was below 1 cpm, but more like at 0.6 to 0.7 cpm. (The deal is structured a way that is not easy to pin down but the guesstimates seem to finally come up to the consensus of the above numbers.)