One of four men arrested in connection to an alleged terror plot to down a passenger plane is suffering mental health issues as a result of his treatment by police during raids last year, a Sydney court has been told.

Khaled Merhi faced Downing Centre Local Court on Monday on an unrelated weapons charge. He has not been charged with any terrorism offences.

His lawyer, Moustafa Kheir, said the 40-year-old intends to plead guilty to possessing a type of Taser without a permit.

But he noted that Merhi "experienced significant physical contact" at the time of his arrest in Surry Hills in late July 2017 and, as a result, has suffered some "mental health issues".

Merhi was arrested with three other men in raids across Sydney relating to an alleged plot to bring down an Etihad plane with a bomb in mid-July last year.

Two of them have since been charged in relation to the alleged plan to target the flight from Sydney to Abu Dhabi.

Khaled Khayat, from Lakemba, and Mahmoud Khayat, of Punchbowl, have each been charged with two counts of acting in preparation for, or planning, a terrorist act.

Lebanon's interior minister has said another brother, Amer Khayat, was to have knowingly carried out the suicide bombing but Australian authorities have suggested he had no idea he was to carry an improvised explosive device.

He caught the flight without his checked baggage after it was rejected at a Sydney Airport check-in counter because it was too heavy. He then travelled to Lebanon, according to the interior minister.

Lebanon in August 2017 said a fourth brother, Tareq Khayat, had moved to the Islamic State stronghold of Raqqa in Syria and become a commander in the jihadist group more than 12 months earlier.

Merhi is scheduled to be sentenced on the weapons charge on March 29.