The offers for the cards listed in this post have expired, so their links have been removed. Click here for the top current credit card sign up bonuses.

Business competition is good for consumers. We've been losing airline competition rapidly for the last five years as Northwest, Continental, and US Airways have been folded into Delta, United, and American.

US Airways and American Airlines have merged. Citi will be the issuer of the credit card for the combined New American Airlines. Barclaycard, which currently issues the US Airways Premier World MasterCard will at some point in the very near future have to discontinue the card.

For that reason, I've recommended that people who want to get a new card get the US Airways Premier World MasterCard with 30,000 US Airways miles after first purchase before it disappears and the chance to earn the miles disappears with it.

The Frontier Airlines World MasterCard® is currently offering its best sign up bonus I've ever seen: 40,000 EarlyReturns miles after spending $500 in the first 90 days of cardmembership.

This huge sign up bonus, especially for such a tiny minimum spending requirement, is enough for:

Two roundtrips anywhere in the US that Frontier flies, including Alaska (30,000 miles).
One roundtrip anywhere Frontier flies, including Central America, Mexico, and the Caribbean (30,000 miles).

Frontier Airlines is the ninth-largest airline in the United States with a hub in Denver and service to Alaska, Mexico, Jamaica, the Dominican

The 50k mile bonus offer is back on the Lufthansa card mentioned in this post until 6/30/14.

The 50k mile bonus offer is back on the Lufthansa card mentioned in this post until 6/30/14.

Some of the offers listed in this post have expired so their links have been removed.

Update 12/17/13: The 50k mile offer is dead.