They do not advertise these challenges but it works as follows.
If you make 30,000 miles in 90 days you get platinum status. This provides some extra perks and your airline miles pile up faster.
On the negative side if a lot of your domestic flying is on AA you wind up crammed in those shitty little Super 80s and MD-80s.

You also have to pay for the challenge dont you???? I think $400 for the platinum???

There is no charge for it.