Is it possible to make a change to an Aeroplan itinerary after it has already begun (ie. you've flown at least one segment of the journey)?
I would presume there'd be a change fee applied.

But let's say you're on a 2 stopover mini RTW (RIP 2 stopover mini RTW). You get to your final stopover (only the flight back home left) and you decide.. hmm.. I'd rather stay here a little while longer.
Is that even possible? (Assuming award availability, etc.)