Hi all,

Visitor from the UA-land here finding myself flying Delta long haul for the first time ever and I want to learn more about how buy ups work with Delta. I was booked in economy on a flight from JFK to Europe. There was an option to buy up to Comfort plus for ($200/2.5k miles) and Premium($780/78k miles) but no buy up option to business via the app. Now the 2.5k miles was a no brainer for even extra legroom so I jumped on it, but then I noticed the option to buy up to Premium was X'd out and likewise business has been closed off. Is there some limit on cabin buy ups and certain types of upgrades that cancel out the ability for future upgrades?

Thanks for any insights on this!