Originally Posted by
FlyAO2
The terms clearly say you can if you use Miles & Cash....use your miles and then pay $5 in cash so that you satisfy the terms:
On Delta flights, you can use one-way Regional Upgrade Certificates on all paid published Main Cabin and Delta Comfort+ ® fares, Award Travel tickets and Miles + Cash tickets on Delta-operated flights, on Pay with Miles tickets, and on Companion Certificates.
Yes, I had no problem applying RUCs to a flight that I paid 20% cash and 80% in miles. Upgrade certificate cleared immediately and as soon as I got off the phone I was able to select D1 seats.