The NPWS legal advisers probably need to review the law after the 13th century. The old Latin maxim
cujus est solum ejus est usque ad coelum et ad inferos was expressly rejected in Anglo-Australian law in
Bernstein (Baron) v Skyviews & General Ltd [1978] QB; [1977] 2 All ER 902. That was a case about an upper class twit who objected to an entrepreneurial pilot who was flying around taking photos of properties and then offering to sell them (the photos) to the owners, The upper class twit claimed that he owned his estate from the core of the earth to the infinity of the heavens (the Latin maxim loosely translated), and therefore anyone who flew above his property was trespassing.
In any case, there is legislation in most of the Australian jurisdictions which effectively accords aircraft a right of innocent passage for the ordinary incidents of flight (which was the answer to the discussion re Avalon BTW). In the case of NSW, it’s subsection 2(1) of the
Damage By Aircraft Act 1952, which subsection says:
No action shall lie in respect of trespass or in respect of nuisance, by reason only of the flight of an aircraft over any property at a height above the ground, which, having regard to wind, weather, and all the circumstances of the case is reasonable, or the ordinary incidents of such flight, so long as the provisions of the Air Navigation Regulations are duly complied with.
The NSW legislature could make a special case for Carnarvon Gorge, but I’m not aware of it having done so, and the Commonwealth rules would apply in any event above a certain height.