Sign up for the US Airways Premier World Mastercard and get up to 40,000 bonus miles, enough for 2 roundtrip flights. You'll get 30,000 miles after your first purchase, plus up 1 mile per dollar on balance transfers within 90 days, up to 10,000 miles. The card also gets you a 5,000 mile discount when booking a flight, which drops a roundtrip domestic flight to as low as 20,000 miles. Other perks including Zone 2 priority boarding on every flight, 2 companion tickets each year, and first class check-in service. The card will earn you 2 miles per dollar on US Airways purchases, and 1 mile on everything else. It also offers 0% APR on purchase and balance transfers for 12 months. Plus, spend $25,000 in a year and you will earn 10,000 elite qualifying miles. There is an $89 annual fee. Bottom-line: the bonus, booking discount, perks and elite miles make this one of the best airline cards.