Through September 8, 2014, American Express is offering a special limited-time signup promotion on the Gold Delta SkyMiles Credit Card — new cardmembers will receive 50,000 bonus miles after spending $1,000 in purchases in the first 3 months of cardmembership. In addition, they will receive a $50 statement credit after making a Delta purchase within the first 3 months. Normally, the Gold card offers only a 30,000 mile signup bonus, so this represents a significant upgrade.

In addition, the Platinum Delta SkyMiles Credit Card is also offering a limited-time promo through September 8, 2014. New cardmembers will receive 15,000 MQMs and 50,000 bonus miles after spending $1,000 in the first 3 months of cardmembership. They’ll also earn a $100 statement credit after making a Delta purchase in the first 3 months. (The Platinum card normally offers a 35,000 mile bonus.)

Some of the benefits of these cards include:

Gold Delta SkyMiles Credit Card

• 2X Miles for every eligible dollar spent on Delta purchases, and 1X miles for each eligible dollar spent for all other purchases.
• First bag free when you check a bag on Delta flights.
• Priority boarding on Delta flights
• No foreign transaction fees
• Annual fee of $95 is waived for the first year

Platinum Delta SkyMiles Credit Card

• 2X Miles for every eligible dollar spent on Delta purchases, and 1X miles for each eligible dollar spent for all other purchases.
• Miles Boost^SM – Earn 10,000 bonus miles and 10,000 MQMs after you spend $25,000 or more in eligible purchases on the Card in a calendar year. Earn an additional 10,000 bonus miles and 10,000 MQMs after you spend $50,000 in eligible purchases on the Card in a Calendar year for a total of 20,000 bonus miles and 20,000 MQMs.
• First bag free when you check a bag on Delta flights.
• Priority boarding on Delta flights
• Annual companion certificate for one roundtrip economy ticket in the 48 contiguous United States
• No foreign transaction fees
• Annual fee of $195

For more info or to apply for these offers, see this link.