For a limited time, Delta and Amex have sweetened the signup bonuses on both their personal and business credit cards, offering 45,000 bonus SkyMiles for opening a new Gold Delta SkyMiles credit card and 55,000 bonus SkyMiles for opening a new Gold Delta SkyMiles Business Credit Card.

Earn 45,000 bonus SkyMiles for the Gold Delta SkyMiles credit card (personal card)
Until December 19, 2011, you’ll earn 45,000 bonus SkyMiles when you spend $3,000 within the first 3 months of opening a new Gold Delta SkyMiles credit card when you apply through www.deltaamexlimitedtimeoffer.com.

This is the same offer that was also available for a limited time about a year ago. It represents a significantly larger bonus–while requiring significantly more spend–over the standard offer available now (30,000 bonus miles after spending $500 within 3 months).

Earn 55,000 bonus SkyMiles for the Gold Delta SkyMiles Business Credit Card from Amex
There’s also an even richer deal available for the business version of the card. Under this offer, you’ll earn 25,000 bonus SkyMiles after your first purchase and another 30,000 bonus SkyMiles after you spend $10,000 within 6 months of opening your account for a total of 55,000 bonus miles.

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Both cards carry an annual fee of $95, which is waived for the first year.

While the deal for the personal card has a certain expiration date, it’s unclear how long the offer for the small business card will last.

Thanks to reader Dave for the tips on these offers.