Mate your a commercial pilot now, any flying that "you" pay for is tax deductible. The confusion is that it's not GST exempt (unless you do it prior to CPL test).
Exactly what GG said. Just because you got away with it, doesn't make it legal. I quote from the ATO:
In order to get a tax deduction....
You must have incurred the expense in the course of earning your assessable income...
and;
Self-education expenses are expenses that you incur when you undertake a work-related course to obtain a formal qualification from a school, college, university or other place of education.
The course must have a sufficient connection to your current employment, that is, the course:
* maintains or improves the specific skills or knowledge you require in your current employment, or
* results in, or is likely to result in, an increase in your income from your current employment.
You cannot claim a deduction for self-education expenses for a course that does not have a sufficient connection to your current employment even though:
* it might be generally related to it (see example 1), or
* it enables you to get new employment.
In other words, just because you are qualified in a profession, doesn't mean your continued study entitles you to a tax deduction.