Thanks for the tip. I logged in and found my itinerary. However, I don't seem to find the option to upgrade to E+.

Would it be this one, which is 'greyed' out?:



I guess I could make a mileage plus account, but I'm afraid it will add this trip to that card instead of my SK *G.

Edit: Or, I suppose it's the 'Travel Options', but that unfortunately gives me this error: "No travel options available at this time, please check back later."