Originally Posted by serfty

I presume you booked with American Airlines, so that would be a SABRE booking reference. Qantas bookings have Amadeus references. These would be different.

I would go to www.Qantas.com/yourbooking and enter the 6 character booking reference you have.

Qantas.com will mainly accept AA SABRE references when they operate flights within the booking.

If entering the AA reference works, note down the Qantas Amadeus reference that will be at the top of the web page.

You may then be able to select seats.

If it does not work online, then call whoever you booked this through and specifically ask for the Qantas Amadeus PNR; once armed with that, you should be able to select seats.