A teen accused of trying to hijack a commercial flight is undergoing brain scans to determine whether he has a neurological condition, a court has been told.
The 17-year-old boy is still in custody after he was tackled down to the ground and arrested over the March 6 incident at Victoria's second-largest airport.
Police allege he climbed through a hole in a fence at Avalon Airport, near Geelong, before making his way on foot to the aircraft about 2.20pm.
About 160 passengers were on board the Jetstar plane, which was due to fly to Sydney.
The teen, who cannot be named for legal reasons, appeared via video link at a children's court hearing on Tuesday, when his lawyer sought a further adjournment.
The lawyer told the court the boy had undergone scans of his brain at a regional hospital and was due to have further scans in late August.
Doctors were assessing whether he had an "organic or physiological neurological condition", the lawyer said.
The boy was also being psychologically assessed later this week, although the psychiatrist had flagged he would not provide a report until the scans were completed, the lawyer said.
The magistrate allowed the case to be adjourned to October so the medical material could be obtained.
Prosecutors also successfully applied to withdraw four charges, including allegations the boy stole two 12 gauge shotguns and possessed a long arm firearm without a licence.
The teen is still facing charges including boarding a commercial aircraft while in possession of a firearm and making threats that he had a bomb in his bag.
During a March hearing, it was revealed a joint counter-terrorism taskforce was investigating the Avalon Airport incident and the boy may have communicated with a foreigner or foreign entity.
Federal police successfully obtained a suppression on the identity of the foreigners, as well as the nature or content of the boy's communications.
The nature or contents of documents allegedly found in the accused's vehicle have also been suppressed.
The magistrate on Tuesday extended those suppressions to the next October court date.
