Originally Posted by
vapilot2004
Practically nothing if the aircraft in question has CG control.
A330, A340 and MD-11 are so equipped as far as I know.
Indeed. It is important that an upgrade costs effectively nothing. The aircraft can move some fuel back if people move forward... as for catering, would 1st class passengers really eat meals left over by other 1st class passengers, or do the 1st class meals simply go bad and get thrown away after they have flown once?