your major problem is that, although what you assert used to be the way allowances were considered, modern generations of pilots and cabin crew use meal allowances to inflate their income when applying for loans. Nowadays, the ATO, banks, employers consider meal allowances to be income. All that is different is that there is a certain amount that the ATO considers to be tax free. the horse has bolted. A long time ago on this issue
The ATO does not consider allowances as income, if they did you would be paying your marginal rate on them. The idea is that allowances are fully expended. And if you are stupid enough to try and claim them as income the portion you are saying that is not being spent could be taxable at your marginal rate.
Any of your Cabin Crew buddies who are using their allowances as income could be in for a nasty surprise if they get audited by the ATO.