Join Date: Jan 2005
Location: New York, NY
Programs: UA, AA, DL, Hertz, Avis, National, Hyatt, Hilton, SPG, Marriott
Posts: 10,111
If I remember correctly, for a Platinum companion, the "PLT" changes to "PLC", and for Gold companion "GLD" to "GLC".
This way the companions prioritize after actual Platinums or Golds on the upgrade list.