Please drop the term "denied boarding". That only applies when the passenger holds a confirmed reservation and does not get to take their original flight because it was oversold.
We don't know whether the PIT-YYZ flight was oversold, and your partner definitely no longer held a valid reservation, so denied boarding is not applicable.
AC still seems to have screwed up; this just isn't a denied boarding situation, and you will make your life easier by not using that term incorrectly.
Moderator note: I believe something similar happened to someone else recently and I will likely merge this thread with that one when I have a few minutes to look for it.
Originally Posted by
Stranger
I still don't understand. First you said that there was a three hours delay on the PIT-YYZ flight. Why did she not take it, or why was she not allowed to board it?
I don't know what's unclear here. The agent at PIT clearly cancelled her ticket before she boarded the PIT-YYZ flight.