Police expect to be at five properties raided in Sydney for two or three more days as they to gather evidence on an alleged terror plot to blow up an aeroplane.
Four men are being held at Sydney police station under special terrorism powers after being arrested during counter-terror raids on Saturday night.
The men have not been charged and could be in custody for days before knowing the specific allegations against them, giving investigators time to gather the evidence they need to finalise any potential case against the group.
Prime Minister Malcolm Turnbull said the raids "disrupted" what appeared to be an "elaborate" conspiracy, adding airport security measures had been increased.
Police said the group were trying to build a bomb they planned to smuggle onto a passenger plane and detonate mid-flight.
It is not yet known what type of plane the group allegedly wanted to target or when they intended to carry out the attack.
Police said they believe they have caught all members of the alleged group, but they have not ruled out the possibility of further arrests.
The five homes - in the inner-city suburb of Surry Hills and the south-western suburbs of Lakemba, Wiley Park and Punchbowl - were targeted by NSW and Australian Federal Police officers in the raids.
The ABC has been told investigators found items that could have been used to make a homemade bomb when they raided the house at Surry Hills.
Increased security measures at airports following the raids caused delays for travellers. International and domestic passengers have been advised to allow extra time for screening and to limit their carry-on and checked baggage, but there have been no official changes to baggage restrictions.
Australia's national terrorism threat level was set to "probable" in September 2014, and remains so after the weekend's counter-terror operation.
"Probable" is third on a scale of five threat levels.
Since 2014, 70 people have been charged as a result of 31 counter-terrorism operations around the country.