A terror plot foiled by Australian police last week was targeted at an Etihad flight from Sydney.
Further details of the plans have been revealed after raids lead to the arrests of four men last week.
Security was stepped up at all airports in Australia following the investigation and passengers are being advised to arrive a minimum two hours before departure of domestic flights and three hours ahead of international flights.
Authorities now say the men, aided by the so-called Islamic State, had earlier failed in an attempt to smuggle a ‘high-end military-grade’ explosive on to an Etihad flight in Sydney on July 15.
But the device did not get through check-in.
They had then switched to plans to build a device that could release toxic gas on an aircraft.
Australian Federal Police (AFP) Deputy Commissioner Michael Phelan said: "This is one of the most sophisticated plots that has ever been attempted on Australian soil."
