Originally Posted by GUWonder

SkyTeam ElitePlus -- which is what NW Platinum status grants too -- entitles the person to access the business lounges operated by any SkyTeam airline upon presentation of same-day international SkyTeam travel boarding pass and validation of SkyTeam ElitePlus credentials; along with that ElitePlus privilege, the ElitePlus member is entitled to bring in one guest too. Class of service is generally not relevant for ElitePlus lounge access (since there are so few SkyTeam first class lounges).