Originally Posted by
greg898
Ah ok, no I wasn't aware of the distinction. Is there any sort of general rule of thumb regarding upgrade space or does it differ in every situation? (And sorry for not seeing this thread before.)
Generally, you need space in the R booking class (you need a subscription to a service like ExpertFlyer to see this, or
rely on the generosity of people on this board to can look it up for you) to be able to confirm an upgrade from any class, although Latitude gets access to additional space that's not publicly visible at all. A flight may have 20 seats for sale in J but no availability in R, or may only have one seat in business class but have that one seat be available for an upgrade (the former being far more common than the latter), or almost any other combination.