CLEARANCE NOT AVAILABLE is a reply you get from ATC only in Australia..
In five flights around the world I have only heard this terminology in this country.
The ATSB have effectively blamed the pilot and the ATC for this accident.
What is dishonestly not covered is the fact that the ATC was also responsible for aircraft in un controlled airspace at the same time. This clearly was a contributing factor.
A famous poster on this site, namely Bindook called the class C airspace above D “ roadblock airspace” He was correct. And now two lives have been lost.
The ATSB needs to re do this report and stop protecting the minister and AsA.