Any track can be inhibited quite easily, and its done often for good reasons. There are a number of states tracks can have for different controller in the system we use. In this case it should have been jurisdiction (green) and it was inhibited (black). For example, a VFR track leaving CTA. We can still see they are around and pass traffic if required, but don't need to be part of our regular scan, they are inhibited and turn black to us instead of green. If we hand off aircraft to another unit that doesn't talk directly to our system (military approach, non taaats towers, across the fir) we inhibit them once we don't need to know about them anymore.
As far as being noticed once the jet was inhibited, with high level sectors only controlling class A airspace, I am only speculating, but would assuming black tracks are very rarely if ever in the scan of any controller. There just wouldn't... or shouldn't be a situation where a black track would be in your airspace by accident (VFR's tooling around at 30,000ft etc) where as a sector controlling ground up would still be looking at black tracks as lower level VFR around and need to get traffic passed around or clearances given etc.
This is just background on why tracks might be inhibited and why they wouldn't be noticed after they have been. As to how this particular track became inhibited, I'll wait for the report like everyone else I don't know anything about this incident, it could be human error, it could be an undiscovered issue with the system we use, but that is why investigations happen to make sure it doesn't happen again. While its an undesirable situation, for Mr Sandilands to generalise Australian ATC as unsafe and label ASA incompetent is unfair in my opinion.
Last edited by mikethepomme; 5th Oct 2012 at 00:55.