This has been going on for many years, at least 6 or 7 that I know of. It used to make sense before the devaluation, but now its not appealing (to me at least). I believe it was MileageJunkie who had spread the word many years ago and at the time it was possible to get 6 miles per dollar. Many FTers (Thank You MJ) racked up millions of USAir/CO miles before the deval. Now its not that easy due to the math, still doable in small amounts. Good luck.