I doubt that the police would lay charges if there were any doubts about his mental status.
The cops don't make that decision. You'll be charged even if you're as nutty as a fruit loaf. It's up to the courts to decide whether you should be punished.
CRIMES ACT 1900 - SECT 205
Prejudicing the safe operation of an aircraft or vessel
205 Prejudicing the safe operation of an aircraft or vessel
A person who, whether on board the aircraft or vessel or not, does anything with the intention of prejudicing the safety of an aircraft or vessel is liable to imprisonment for 14 years.