Originally Posted by
transpac
I believe you are mistaken, at least in the case of UA/MP. They are not required to do any such thing. There have been many, many first-hand reports, in the case of schedule change/cancellation on award tickets, where UA/MP have simply canceled the award ticket, redeposited the miles (without any applicable fees) and refunded any associated fees.
I haven't seen many of the reports you mention. I have seen some reports of people being rebooked on UA metal under similar circumstances. I believe that any ticket issued (whether paid for with cash or miles) is governed by the contract of carriage - which in most cases outlines that the carrier will attempt to rebook you an on acceptable alternative.
There may be cases where they won't or can't.