Upgrade is are defined as a Travel Extra. Travel Extras are chargeable services you can add to your booking on SAS operated flights.
SAS upgrade is an option to upgrade your comfort on your trip to SAS Plus or SAS Business.
You have three possibilities to buy an upgrade
SAS Upgrade to SAS Plus and SAS Business includes Business check-in, access to SAS Fast Track and SAS Lounges and priority boarding at selected airports, as well as extra comfort and inflight meals on SAS operated flights.