Amex has recently increased the welcome offer for several of the co-branded Delta SkyMiles.
Here is the list of the current offers:
Delta SkyMiles® Gold: 80,000 Bonus Miles after you spend $3,000 in purchases on your new card in your first 6 months of card membership. (The previous offer was 65,000)
Delta SkyMiles® Platinum: 90,000 Bonus Miles after you spend $4,000 in purchases on your new card in your first 6 months of card membership. (The previous offer was 85,000)
Delta SkyMiles® Reserve: 100,000 Bonus Miles after you spend $6,000 in purchases on your new card in your first 6 months of card membership. (The previous offer was 95,000)