Sign up for the US Airways Premier World Mastercard and get up to 40,000 bonus miles when you make your first purchase and pay the $89 annual fee. 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 (this means your bonus miles can be redeemed for 2 free flights!) Other perks including a free checked bag for you and up to 4 companions, Zone 2 priority boarding on every flight, and first class check-in service, and a companion certificate good for up to 2 guests to travel with you on a US Airways flight at $99 each. The card will earn you 2 miles per dollar on US Airways purchases, and 1 mile on everything else. Plus, spend $25,000 in a year and you will earn 10,000 elite qualifying miles. Bottom-line: the bonus, booking discount, perks and elite miles make this one of the best airline cards. See our ranking of the top 5 credit card signup bonuses for additional options.