After a long hiatus, the 100% bonus offer on purchased miles from US Airways has returned. If you have ever considered purchasing miles before, this is the time to do it and this is the program to invest in.
$1479.50 (50,000 miles @ $0.0275 per mile + 7.5% tax) will get you 100,000 miles. That 100,000 miles translates into a business class ticket from North America to Europe or will almost pay (120,000 miles required) for a first class ticket from North America to Asia via Europe (with a stopover allowed).
As Gary points out, another advantage in redeeming US Airways miles is the option to hold an award for three days without having the miles in your account. That means you can call up US Airways, confirm availability for the dates you wish to travel, put the reservation on hold, then purchase the miles (which quickly post to your account).
The promotion runs through June 30th and your US Airways account must at least 12 days old in order to purchase miles. You are also limited to purchasing 50,000 miles with this offer.