Extra screening remains in place at airports around Australia, after police say they foiled a terrorist plot to bring down an airliner.
Four people remain in custody following raids over the weekend in Sydney.
There are reports the plan involved releasing a toxic gas into the cabin.
The Australian Prime Minister Malcom Turnball has described it as a "major joint counter-terrorism operation".
New South Wales Police Commissioner Mick Fuller said the timing was crucial: "The reality is, with terrorism, you can't wait, you can't wait until you put the whole puzzle together".
"You do have to go early because if you get it wrong, the consequences are severe."