Originally Posted by
xjaehyun
If there's availability in PS and D1 on transcon flights, you're eligible for both. However, if you're booked in main cabin and you use an RUC, you'll get upgraded to PS and you'll be on the upgrade list for D1. If you booked PS and you use an RUC, you'd get upgraded to D1. This was confirmed by a phone rep last week.
Same as GUCs. That’s why I like KLM for now with only 2 classes of service. Although last year I did surprisingly clear D1 once at exactly T-24 from MC from Europe back to USA. .