bobtait replied the topic: Do I have to re-purchase the books if I have the old ones already?
It depends on how old they are. You should get by with Nav and Performance but you will need to check our errata page for changes in those publications.
However, when it comes to Air Law and HPL there have been quite a number of major changes in the last six or seven years. Again, there are posts on our errata pages but I would recommend you consider getting the latest version of Air Law and HPL - either hard copy or e-text.