NOTE: For flights where First or Business Class is not offered or available, passengers may travel in a lower Class, in the applicable booking code for that lower Class.

Where the applicable booking class for the lower class is not available,
Passengers travelling on First Class Fares may book Y class

Passengers travelling on DONE* Business Class Fares may book B class

The fare for the highest Class used applies, without compensation.

Exceptions
i) for AA services within the USA ...
ii) for US services within TC1 ...
iii) for services within the Middle East, where no Business Class is offered, Business Class passengers may book and travel in A Class on QR, subject to availability. This provision does not apply on any flight where Business Class exists but is unavailable for booking”