Two father and son teams will remain in custody for at least the next week after a Sydney magistrate granted Federal Police seven more days to interrogate them.
The four, reportedly all family members, are accused of plotting to bring down a plane bound for the Middle East with an Islamic State inspired home-made bomb.
They were arrested during raids on five properties at Surry Hills, Lakemba, Punchbowl and Wiley Park on Saturday with police still at the addresses today.
There are reports a meat-mincer and grinder have been seized from the terrace at Surry Hills along with handwritten notes, two phones, an iPad along with car rego and insurance papers and a couple of cars.
BEEFED UP AIRPORT SECURITY:
Travellers heading around Australian and overseas are being warned to expect delays and pack light.
A two-hour check-in time is now in place for domestic passengers and three-hours for international travellers.
The extra check-in time is for "additional scrutiny" and security experts say the arrangements will likely be in place for the foreseeable future.