The fresh allegations came in court documents released by a children's court on Thursday, a day after the now-19-year-old opposed an application to have his case heard in a higher court.
It's alleged the teen, dressed in high-vis clothing and carrying a tool box, sneaked his way onto the Jetstar flight at Avalon Airport in Melbourne's southwest shortly before 3pm on March 6, 2025.
The teen, who appeared sweaty and clammy, told cabin crew staff he had bombs in his bags and he needed to go into the cockpit, the documents said.
It's alleged he pulled out parts of a shotgun from his jacket and was in the process of putting them together when other passengers and crew intervened and restrained him.
The teen allegedly told some of the bystanders they were good people and he respected them after he was tackled to the ground.
When police arrived and searched the teen, they allegedly found a bomb diagram plan and a to-do list that said he needed to "make sure all weapons are assembled and stored".
The list also stated he needed to "check explosives", "work out disguise" and "wear safety glasses", the documents said.
It's alleged the teen also had a shotgun broken into three parts, nine shotgun cartridges, three knives, three Molotov cocktails and a teddy bear.
A Hungry Jacks receipt from 12.25pm and a drink from the fast food chain were also located in his car, the documents said.
The teen, who was 17 at the time, has been charged eight offences, including attempted hijacking and prejudicing the safe operation of an aircraft with intent to kill.
The maximum penalty for those more serious offences is life in prison.
At Wednesday's children's court hearing, prosecutors alleged the teen held a political or ideological motive as they applied for the case to be heard in the county or supreme courts.
The prosecutor argued the penalties available in the children's court - a maximum sentence of a two-year supervision order - were inadequate to reflect the seriousness of the alleged crime.
The teen's lawyer instead pushed for the case to remain in the children's court, arguing a jury could not fairly and impartially decide on the case.
The lawyer also flagged a potential mental impairment defence, saying the teen's mental health had deteriorated in the lead up to the alleged attempted hijacking.
The magistrate will decide in June whether to uplift the case to a higher court.
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