Because subsection (1) of section 9A of the Civil Aviation Act is cited so frequently as the justification for just about anything, few people get to subsection (2), which says:
(2) Subject to subsection (1), CASA must exercise its powers and perform its functions in a manner that ensures that, as far as is practicable, the environment is protected from:
(a) the effects of the operation and use of aircraft; and
(b) the effects associated with the operation and use of aircraft.
Subsection (2) has profound theoretical implications that are generally not realised practically, as a consequence of politics.