eurousair ,
I first signed up for the Silver Challenge, and then later heard about and signed up for the Gold Challenge. Next, I called to see which offer I would now be signed up for. The first rep told me the Silver offer, but then transferred me to someone else who said I would be signed up for the Gold Challenge since that was the last offer I signed up for. She said that by signing up for the Gold Offer deleted out the Silver offer. So US d/m reps really don't know how this will work, but perhaps I'll have to just see which one I get. But punch the promotion code in for the gold offer, and try it. Who knows what will actually happen inside US's computers. Reps also give out differing data, from call to call, regarding the combinability of other bonus mile offers. E.g. the book 3 online, and the one where you can earn 20K miles for booking high yield tickets. You get a different story each time you call.