A Virgin Airlines flight arrived 15 minutes later than scheduled after its pilot heard Paul Sant broadcast the message "Go around" on a publicly accessible distress frequency on October 27, Melbourne Magistrates Court was told on Monday.

The pilot aborted the landing after hearing the message, and made a loop in the airspace above the airport before landing without incident.

During a bail application, defence counsel Pern Chaya said Mr Sant, 19, was autistic, and after being scared during a week in custody, understood the seriousness of his alleged offending. "He has now learnt how serious this is and that this is not a joke," Ms Chaya said.

Mr Sant was watching the airport from the Sunbury Road viewing area when he saw the Virgin flight's landing gear come down and then broadcast the message, AFP officer Jonathan Croft told the court.

The incident caused major concerns to the airport's control tower, Constable Croft said, and was considered a "major aviation incident" that had the potential to threaten people's safety.

He alleged the message was one of several Mr Sant had made on the frequency on October 25 and October 27, but it was the the only one a pilot had responded to by taking action.

On October 27 Mr Sant also made two mayday calls, the officer said, claiming an aircraft was about to crash into the Maribyrnong River and later stating the plane had "gone down".

Authorities checked with the pilot of the aircraft and found it had safely landed at Coolangatta in Queensland, the court heard.

Mr Sant was arrested last week at his Rockbank home and was charged with four counts of endangering the safety of an aircraft in flight, an offence that carries a maximum of 20 years in jail. He has also been charged with one count of transmitting interference that could endanger the safety of another person.

Federal police allege the teenager advised pilots to "go around" and "abort takeoff" on October 25, but that those instructions were ignored by the pilots of Jetstar and Qantas aircraft who were both preparing to land.

Federal police and prosecutors opposed Mr Sant's bid for bail over concerns he would offend if released from custody, he would contact witnesses and he would destroy evidence.

Constable Croft said police were yet to find the radio Mr Sant had allegedly used when he transmitted the messages, and that he had told friends he had thrown the device into a lake. Police were preparing to scour the lake, the court heard.

Deputy chief magistrate Jelena Popovic said she was satisfied the prosecution case was a strong one, but wanted Mr Sant to undergo psychological testing before she ruled on his bail.

She said she had concerns he could spend a long time in custody awaiting a possible trial if ultimately he was not sentenced to jail given his potential mental-health problems.

Ms Popovic will rule on Mr Sant's application on December 16.