'We've taken this threat very seriously,' Mr Colvin said.'You should infer that we think this was credible and there was an intention, and there was quite possibly a capability as well.' Airports across Australia are experiencing long queues after Prime Minister Malcolm Turnbull warned of heightened security measures across the nation.
Residents living near the Surry Hills home, just metres from the Redfern Mosque, were evacuated while the bomb squad worked to remove the 'explosive device'.
A kitchen mincer is believed to be among the everyday items the alleged attackers used to form a lethal device, according to the Herald Sun.
The apparatus was reportedly 'ready to go' as counter-terrorism police stormed properties across the city's west and inner-east.
As police continue to search properties linked to the two families, a letter also found in a bin at one home in Lakemba, in the city's west, had links to another home raided in Surry Hills, the Daily Telegraph reports.
While the full extent of the alleged ISIS-inspired conspiracy is not yet known, so far it is believed the men - including the two father's aged in their 40s - planned to gas all passengers on board before detonating the bomb.
NSW and Federal Police swooped on five properties in the Sydney suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl on Saturday afternoon and found a 'considerable' amount of material.
But police won't say if they discovered an actual explosive device.
Airlines fly from Jakarta to Australia daily, with direct flights to all capital cities.
According to The Australian the four, who are all related, allegedly made a 'non-traditional' device designed to kill passengers with a sulphur-based gas.
He could be heard saying 'they bashed me.' When asked by who, he answered 'police'.
When asked why he was being arrested, the man mumbled 'I don't know nothing'.
Police have discovered flight details for a Jakarta to Sydney flight as investigations continue into the arrest of two father and son duos over an alleged plot to blow up a plane.