Originally Posted by
MSPeconomist
If you can now use GUCs on KE operated flights, this is new. You can use DL miles to upgrade from FULL Y fares to business class under the SkyTeam mileage upgrade award program.
From DL's site:
https://www.delta.com/content/www/en...-upgrades.html
"
Finding flights: Upgrade Certificates can be used on any Delta-operated flight, and select partner-operated flights with KLM, Air France, Virgin Atlantic, Korean Air and Aeromexico."
So its there under the cert upgrade eligible carriers.