Originally Posted by
MSPeconomist
IIRC officially she must be on your PNR (check the T&C on your RUC) but unofficially people seem to have done this successfully by calling DL.
I suspect DL is more generous with Diamonds than Plats regarding this rule but OP has nothing to lose by asking.
May be redeemed for the named Medallion member and up to one travel companion in the same reservation. The named member and the companion will each require a separate certificate.