Usually, we're not so big on buying miles because the price per mile isn't good value. But what if your airline gives you a 100% bonus? 

Through May 31, 2013 for every mile you buy, US Airways will give you an additional mile for free.

Buy 50,000 miles for $1881 (including tax) and you get an additional 50,000. You only need 90,000 miles to fly to Asia round-trip from the US in business class, for example, on airlines in the US Airways-affiliated Star Alliance (such as Singapore, Asiana, and Lufthansa; see US Airways' partner award chart.

US Airways is planning to exit the Star Alliance following the completion of its merger with American, but the exit date is not expected until 2014. Until then, the US Airways award ticket prices are the most affordable of any domestic airline.

These miles could take you to Australia in business class for 110,000 miles (most other airlines charge around 140,000-150,000 for business class). European business class flights clock in at 100,000 miles roundtrip, and roundtrips to Africa are 120,000 miles.

One of the best ways to search for US Airways award availability is actually to use its competitor United Airlines' site, which features accurate access to most "Saver" awards. Once you see the availability on United's website, you then call US Airways and tell them the exact flights you want.

Needless to say, you'll also have to pay taxes on the "free" ticket, which could set you back another $100-300 or so, depending on your destination. And you might have trouble finding the exact dates you prefer, since free seats are capacity controlled, so it's a good idea to see what the availability is before you buy the miles. But you still come out on top, saving quite a bit on travel in business class.

Still, you could pick up a business class ticket for less than $2,000 with this method. Business class tickets to Australia can cost up to $10,000 meaning buying these miles can save you more than 75%.

You needn't buy 50,000 miles if you already have miles in your account. The minimum purchase for the bonus is 5000 miles for $188 (including tax), which makes this a great way to top up your account. However, if you have zero miles, you can still attain a business class ticket simply by buying the miles with this promotion. Note that your Dividend Miles account must be at least 12 days old to qualify.

And eventually you'll be able to transfer these miles to your American Airlines Aadvantage account when the two airlines fully merge.

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