The men accused of crafting a bomb plot to bring down a plane were receiving direction from a senior member of Islamic State in Syria, the Australian Federal Police have revealed.
Police described two terror plots as "the most sophisticated plots ever detected in Australia" as two men prepared to face court over planned attacks on terror charges this morning.
AFP Deputy Commissioner Michael Phelan said the alleged would-be terrorists had planned two attacks.
Elements of an improvised explosive device (IED) was sent by Isis operatives through international air cargo to the accused men, who police claim used the Isis commander's instructions to assemble it, Phelan said.
The device was to have been detonated on an Etihad flight out of Sydney on July 15, AFP allege, but the plan was aborted.
"We will be alleging that a fully functioning IED was to be placed on that plane on July 15," Phelan said.
"There is a little bit of conjecture as to why it didn't go ahead on the 15th. We certainly would be alleging that it didn't get past check-in."
Police said a planned second attack would have used an improvised chemical device to release "highly toxic hydrogen sulphide".
Phelan said the device, which was very difficult to make, was "fairly well advanced, but not enough to be a fully initiated device".
He said joint counter terror officers "completely disrupted" both plots.
"Not only have we stopped the IED that was believed to go on the plane but we have also completely disrupted the intended chemical dispersion device and we believe we have got all of the necessary components of that device as well," he said.
NSW Police Deputy Commissioner David Hudson said the charged men had been put in contact with the senior Isis figure through the brother of one of the men.
"We will be alleging in court that the communications were commenced around about April," Hudson said.
The components of the two explosive devices were found dispersed between a number of premises that police raided on July 29.
Earlier, details emerged about how close alleged would-be bombers got to carrying an explosive device aboard an international flight from Sydney, as two men have been charged with terrorism offences.
The NSW Joint Counter Terrorism Team has charged a 49-year-old Lakemba man, Khaled Mahmoud Khayat, and Mahmoud Khayat, a 32-year-old Punchbowl man, with two counts each of acts in preparation for a terrorist act.
The maximum penalty for the offence is life imprisonment. Both men are scheduled to appear at Parramatta Court this morning.
As the two men prepare to face court, the Daily Telegraph reported an unwitting passenger may have been used to smuggle a bomb on a plane destined for the Middle East.
The plot to have the device detonated "without [the bomber] knowing they were part of a suicide mission" was aborted.
On Thursday afternoon, Fairfax reported the device made it as far as Sydney International Airport terminal's check-in area and that a passenger was "queried about the weight of the luggage at the check-in counter and learned it was too heavy".
The report suggests the bag was never checked in.
Neither NSW or Australian Federal Police would comment when contacted by news.com.au because the investigation is ongoing.
A 50-year-old man, Abdul Merhi, was released from police custody on Tuesday August 1, without charge. One man remains in custody and police have seven days in which to conduct inquiries.
Australian intelligence received word last week about an apparent plan to smuggle an explosive onto a flight, which led to dramatic raids over the weekend.
Police have remained tightlipped about their investigations, however they are working with Etihad Airlines, who are assisting with inquiries.
On Tuesday, Abdul Merhi, 50, was released without charge. His lawyer, Moustafa Kheir, said his client felt he was "in a movie" when he heard of the allegations.
"It's a very serious allegation to have against you," Kheir said. "It's just unfathomable that he would be associated with anything like this."
"He just wants to go back to as normal life as possible now," Kheir said.
Police have called for photo identification to be reintroduced for issuing domestic plane tickets and for all airport employees to go through security screening.
The peak body for pilots has also called for greater security.
AusAlpa president Captain Murray Butt backed calls for all passengers to be required to produce photographic identification as they must in the US.
"We certainly don't want to alarm the public," he said in Sydney. "But we want to make sure we're providing the best service that we can and the safest service that we can."
Police are still searching properties in Lakemba, Wiley Park, Punchbowl and Surry Hills for evidence.
Prime Minister Malcolm Turnbull addressed the media yesterday afternoon. He said the alleged plot was foiled but Australians should remain vigilant about the threat of an attack.
"The threat of Islamist terrorism is a global one," he said.
"As I've said many times, nowhere is far away from anywhere else in the age of the internet.
"Our enemies, those terrorists, those Islamist terrorist organisations are global and they are connected."
He also said there will be fewer delays at Australian airports for travellers after authorities disrupted the aviation terror threat. Asio has moved to restore the aviation threat level to what it was before the alleged plot to bring down a plane was uncovered.
That means a return to normal check-in times for travellers, however plainclothes officers and extra training for cabin crew will remain in place.
Although there will be fewer flight delays, Turnbull said it didn't mean people should become complacent.