Originally Posted by maalloc

They do seem to have lots of leeway.
Data point from today: I just had a GVA <-> Asia fight canceled, and various options were openly considered while trying to find a replacement itinerary: ex-GVA, ex-CDG, ex-LYS. For sure those are usually priced very differently.

They didn't bat an eye when I took opportunity of this clean slate to change the travel dates by 10 days.

Originally Posted by tbaiyun

Per policy when I discussed this with the PSL agent a while ago, it it 100 miles apart (160 km) from your original departure/arrival city, meaning something like MRS and MPL, or LUX and BRU, BSL and SXB, etc. However, my recent experience is that this was not quite enforced as I asked them to move me from CDG-YQB to CDG-YUL-YOW, and they changed it without any question (of course, there was a KL intra-EU flight cancellation on the whole itinerary that entitles a free change).

I would say with PSL, when there is an involuntary change and we are entitled for a reroute, most of the time they will just comply per your request with no extra charges. On the other hand, when it is a voluntary change and the system shows there is a fare difference to charge, they would never waive it unless it is less than $1.