However many ways you look at the tax situation, I would urge all of you to stop burying your heads in the sand and hoping this problem will go away, it won't.
As I said earlier;
There is a very easy way to tell if you are liable for tax.
Ask yourself this simple question; am I happy for the tax authorities in the country where I work to know all about my financial arrangements?
If you answer NO, then you are breaking the law in that country.
This rule applies wherever your company has its headquaters, wherever you come from, wherever your family live and wherever you work. It makes no difference. We are ALL obliged to pay tax, somewhere.
There are locally employed German crews, in Germany, who are under the false impression that they don't need to pay tax in Germany because easyjet and Ryanair have their headquaters outside Germany. Just how naive or blatantly stupid are these individuals? If you think you are being clever now, just wait until the fine hits you.
For German in the above paragraph, inseret your own nationality.
Once again, read the question above.