Ulf Kutzner wrote:

Why? If I have a NW ticket for a NW flight number, they should accept
it. Fullstop.
A ticket is a ticket is a ticket. True or false?

It sounds like it was a NW ticket for an NW flight number on a AS code
share. This means it was probably an AS plane with an AS flight number,
that also had an NW flight number.

According to them, they said AS said there was no payment from NW for
the seat.


With a NW issued ticket for an AS flight number, the story *might* be
different.

The point is that it probably also had an AS number as it sounded like
this was an AS flight that AS let NW sell seats on. If they had bought
an AS ticket, it would be difficult for AS to say that AS didn't pay for
the seat.



but that fare might have
been higher (or lower). I assume you bought the NW one due to a lower
fare, as it doesn't sound like you have FF issues. Also, it isn't just
an E-Ticket issue. Having a paper ticket doesn't stop them from changing
the flights.


But makes it easier for the passenger to prove what was in the contract.

That depends. The NW ticket would have the NW flight number. It is
possible that NW changed the NW flight to another airline, as the
customer indicated they were told NW changed them to another airline.