AA use sabre and BA use Amadeus.

Its best to phone AA up and ask them for BA / amadeus reference number

1.
When you book your flight, get your GDS reservation code. This is usually different from the airline confirmation number, but a booking agency is likely to give it to you. It is made up of six letters and/or numbers.

2
Determine which system was used to book your flight. Reservation codes starting with 1, 2, 3, 4, 5, X, Y, or Z are from the Amadeus system. Codes starting with anything else are from the Sabre system. Each system has its own website to check flights online.

3
If you have an Amadeus code, check your flight by going to www.checkmytrip.com. Enter the GDS reservation code and the passenger's last name.

4
If you have a Sabre code, ceck your flight by going to www.virtuallythere.com. Enter the GDS reservation code and the passenger's last name.