So I've heard several people on this forum claim it's an AA issue.
American Airlines denies any wrongdoing.
On one hand, this is a vague sentence that can mean anything. On the other hand, improperly issuing an eticket would constitute wrongdoing imo, so I'll assume AA is telling the truth and it's not their fault.
Additionally, if it
is an AA issue, AC itself acknowledges that it's no blameless:
Air Canada acknowledged that its employee at the check-in gate should have caught the error before issuing a boarding pass to Kerri Moore.
Regardless of who caused this pax to be unable to be boarded, how do you defend AC's pulling off already-boarded pax because one member of their travel party -- who allegedly was okay with being left behind -- is left behind?