Khaled Merhi, 40, was one of four men arrested last year over an alleged conspiracy to bring down with a bomb an Etihad plane bound for the Middle East from Sydney.

He was never charged with terror offences but, after a raid on his Surry Hills property, he was accused of possessing a weapon without a permit - a charge to which Mr Merhi pleaded guilty.

He told police he used the homemade device to turn a gas stove on, according to a statement of facts tendered in court.

Magistrate Jacqueline Milledge dismissed the charge in Downing Centre Local Court on Wednesday after police prosecutor Amin Assaad said the object was essentially an improvised fly swatter.

Sen Sgt Assaad said the effect of the device was 300-times less than the voltage of a NSW Police Taser, and the time Mr Merhi had already spent in custody was sufficient penalty for the offence.

The magistrate acknowledged the case had significantly affected Mr Merhi, who was injured and detained for more than a week during his arrest.

She took into account the effect of media publicity, and noted it was Mr Merhi himself who brought the object to the police's attention.

"Be careful who you're mixing with in the future, Mr Merhi," she said after dismissing the charge.

Two of the men arrested in the July 2017 raids were charged over the alleged plan to target the flight from Sydney to Abu Dhabi.

Khaled Khayat, from Lakemba, and Mahmoud Khayat, of Punchbowl, are each accused of acting in preparation for, or planning, a terrorist act. The fourth man was released without charge.

Australian Associated Press