Originally Posted by
ISTFlyer
You could call AA or even use Powetools/Bookwithmatrix -> AA.com through ITA Matrix and pay online.
As a reminder AA's schedule change, cancellation and COVID-19 flexibility policy is different than BA's.
If you would like to book in BA stock, you could still call Bremen or another contact center outside the UK or use a travel agent.
I've just called AA and the guy there says that his system can only accept six segments in building a multi-city itinerary, whereas mine has seven. Frustrating.