An unsuspecting passenger was reportedly to be used to take a bomb onto a flight out of Sydney in the terror plot police say was foiled on the weekend.

“The person was going to be blown up without knowing they were part of a suicide mission,” a source told News Corp Australia.

The idea was abandoned when it was decided the device, reportedly a meat mincer, would be too heavy to go unnoticed in the carry-on luggage.

The Australian Pilot’s Association are calling for private security contractors to be replaced and baggage checks by government security.

Little has been confirmed officially but authorities have said the plot involved plans to “bring down” an aircraft using an “improvised device”.

Police spent Wednesday searching a terrace in Surry Hills and removed what sources describe is an item of interest.

The alleged plot has led to heightened security at airports across Australia.

Properties in Lakemba, Wiley Park, Punchbowl and Surry Hills have been investigated in search of evidence.

Four men were initially arrested in Saturday night’s raids, but Abdul Merhi, 50, was released without charge on Tuesday night.

Three men remain in Australian Federal Police custody after the AFP was granted the power to hold them for up to seven days, which expires on Sunday evening.

Mr Merhi’s solicitor Moustafa Kheir says he’s concerned his client’s identity was revealed and has declared he’ll “review what basis police had to do what they did”.

My client Abdul Merhi has been released without charge. Tough few days, but he's relieved the truth is out. I will review police action.

— Moustafa Kheir (@Mouskheir) August 1, 2017