I'm not sure with JAA ATPL, I'm an CAA ATPL Holder. For CAA UK syllabus it consists of two different phase, CA6 and CA2. CA6 covers Navigation,Instruments,Radio Aids,Flight Planning, Meteorology Theory and Meterology Practical whereby CA2 covers Perfomance 'A' and Loading. I'm very sure that Perfomance 'A' is a must for every airlines.