Delta Business Card Upgrade Offers
1. Gold → Platinum
感谢评论区 amex delta 升级offer link 3.23 Update 更好的奖励 - #18，来自 偷佬肆
Earn 50,000 Bonus Miles and a $200 Statement Credit
after you upgrade to the Delta SkyMiles® Platinum Business American Express Card and spend $3,000 in eligible purchases within the first six months of Card Membership.1 Now
when your business is ready to travel, you can earn more miles to get you there.
Earn 30,000 Bonus Miles and a $100 Statement Credit†
Upgrade to the Delta SkyMiles® Platinum Business Card and earn:
- 30,000 Bonus Miles
- $100 Statement Credit
** Requirement: Spend $6,000 in purchases on the Card in the first 6 months of Card Membership.†
2. Platinum → Reserve
Earn 40,000 Bonus Miles and a $200 Statement Credit†
Upgrade to the Delta SkyMiles® Reserve Business Card and earn:
- 40,000 Bonus Miles
- $200 Statement Credit
Requirement: Spend $10,000 in purchases on the Card in the first 6 months of Card Membership.†
** Personal 版本讨论**
Note
1.需要woc
2. 可以双吃或者三吃， 每次升级/降级，酒店报销会重置 
3.Business platinum似乎不能降级business gold, 客服解释是25年开始一些payment相关的feature导致的。
4. 连续升级可以连吃升级offer
一个循环的话除了升级奖励
个人卡blue-> gold-> platinum-> blue一个循环 ，650年费获得100+150+200=450酒店报销+550刀+65k点+基友票。
商业卡可以gold->platinum-> reserve 循环 650年费获得150+200+250=600酒店报销+300刀+70k点+集邮票
