Originally Posted by
TerryK
It reads to me that OP has VS O class on return, not DL O class. It is main cabin. He/she is asking in the wrong forum.
No, awards are booked as prime flight number. Thus since OP is on DL metal, he's booked on a DL flight number and in O class. This is Delta 1.
The VS system is confused and labels it Main cabin since O would be main cabin if booked as a VS flight.