Originally Posted by TRAVELSIG

For SQ upgrades call M&M or have your travel agent do it for you (they can do this as long as you authorize them and give them your PIN).

IIRC with Miles and More to upgrade on SQ from economy to business you need to have only B or Y classes.

I have never attempted an upgrade from economy to business however from D to F works fine as long as it is not an A388 (i.e. there usually is space and it does work).