US Airways and American Airlines have merged since the publication of this post, so it is no longer valid. Click here for the top current credit card sign up bonuses.

US Airways Double Miles Promotion

According to this milepoint thread and this FlyerTalk thread, there is a recent offer to get double miles on any US Airways or US Airways Express flight purchased with a MasterCard or US Airways Dividend Miles MasterCard. To exploit this offer, you must book by October 31.

You must register for the promotion in advance through this link.