Randy Peterson also has a book out called the official frequent flyer guidebook. it tells you what you can use for what carrier and what gives the best mileage accruel.I thinkyou can purchase it from his websight flyertalk too! if not then check with Barnes and noble. according to this book the only cc that delta uses for ftp miles is American express and you can also convert your diners club points into DL miles. if you need to know anything else let me know and I cna tell you what it says in the book. I also get the inside flyer magazine from Randys websight too. if you have mci as your long distance carrier you can accrue miles that way as well.