Question on behalf of a relative who is travelling at the moment. Itinerary Europe to Canada and back (booked with Lufthansa, sold as LH and AC flight number appropriate to whichever metal being used per flight), including a flight originally booked as Vancouver to Halifax on AC. This was cancelled 6-8 weeks ago and an alternative was offered and accepted - Vancouver-Ottawa-Halifax. When my relative tried to check in for this flight the other day it emerged that the new routing hadn't been ticketed, and he was denied ability to check-in. Several phone calls later and AC put him on an overnight Vancouver - Halifax. Upshot is he arrived approx 14 hours later than booked, and in the midst had a lot of inconvenience and stress (and declined the airlines attempt to charge him $500!)

Questions are: what can he do about this? He must be entitled to compensation but is this as "involuntary denied boarding" or something else?

Thanks