Police continue to search a home in Surry Hills, Sydney. Credit:AAP Image The conversation quickly turned to building a bomb to smuggle onto a passenger jet. "Thanks be to God," Mr Khayat wrote in reply to one message detailing instructions on chemical reactions. The alleged plot, outlined in detail on Friday following the charging of Mr Khayat and his 32-year-old brother Mahmoud, has all the hallmarks of what experts have identified as Islamic State's latest trend in depravity: "remote-controlled" or "virtually-planned" attacks in which IS operatives give step-by-step instructions to seas supporters on how, where and when to carry out an attack. With the help of the IS controller, high-end military-grade explosives were posted to Mr Khayat from Turkey and instructions were subsequently given on how to build the bomb.

Bomb squad officers and heavily armed police searched a unit on Sproule Street, Lakemba, following the arrest of four men. Credit:Michele Mossop Police allege Mr Khayat and younger brother Mahmoud worked away for three months, eventually creating a product that was "fully functioning". But, miraculously, the bag was never checked in on July 15, possibly because the luggage was too heavy. An injured Khaled Merhi is taken away in an ambulance after being arrested in Surry Hills on July 29. Credit:Seven News Mr Khayat took it back to his Lakemba home and his brother boarded his flight, unaware he almost became the patsy in Australia's most elaborate terror plot.

"This is one of the most sophisticated plots that has ever been attempted on Australian soil," AFP Deputy Commissioner Mike Phelan said on Friday. Khaled Khayat allegedly took a bomb back home to Lakemba after it was too heavy to be checked in on an Etihad flight. In an astonishing revelation, Mr Phelan said that police knew nothing about the men or the plot until 11 days later, when the group were allegedly midway through a second attempt. US and British agencies tipped them off on July 26 after intercepting communication from the IS operative providing direction on a second plan, this time to build a "chemical dispersion device" to release colourless toxic gas. Khaled Khayat was arrested in Surry Hills over the terrorist plot.

The men were immediately put under surveillance until July 29 when they were arrested in six raids across Surry Hills, Lakemba, Punchbowl, Wiley Park and Bankstown. Those raids unc ed every element of the first explosive device, by then dismantled and allegedly spread across Mr Merhi's Surry Hills terrace and Mr Khayat's Lakemba unit. Mahmoud Khayat being arrested in Lakemba on July 29 as part of raids over an alleged plot to bring down a plane. Credit:Seven News Mr Merhi had set up a business, Khaleds Powder Coating Services, two days after the first attempt, possibly as a front to obtain chemical materials. In the Surry Hills and Lakemba homes, police found precursors, chemicals and evidence of experiments and reactions that point towards a complex plot to build a device to disperse hydrogen sulphide.

"There were certainly precursor chemicals that had been produced and some of the components had been produced but we were a long way from having a functioning chemical dispersion device," Mr Phelan said. Messages between Mr Khayat and the IS controller reveal discussions to put the gas device in a crowded space, possibly on public transport. It's understood the Middle East-bound Etihad flight was opportunistically targeted by Mr Khayat for the first attempt after he realised his brother had genuinely booked a seat on it. Mr Phelan said he believes the first bomb would never have made it through security, had it been checked in. He said police created a mock of the IED and did "penetration testing" of airport security and had a "100 per cent success rate" of it being detected.

"We are extremely confident given the systems we have in this country that the IED would have been picked up," he said. The Khayat brothers were charged on Thursday night with planning two terrorist acts – one between April and July 16, one between July 16 and July 29 – after spending almost six days in custody under a special terrorism detention order. Neither applied for bail in Parramatta Local Court on Friday and they will reappear in court in November. Khaled Merhi remains in detention and is expected to be charged the weekend. His 50-year-old brother, Abdul Merhi, was released without charge on Tuesday after 70 hours of questioning. He maintains he had nothing to do with the plot.

The brother who flew to Abu Dhabi has not returned to Australia and is not facing charges. Asked if he was "surprised" that such a sophisticated plot initially escaped police attention, Mr Phelan said "nothing surprises me". "If it hadn't been for the great work our intelligence agencies and law enforcement a very quick period of time then we could very well have had a catastrophic event in this country," he said. The plots Loading



Plot A: The bomb on a passenger plane Islamic State operative sends components of an improvised explosive device from Turkey to Australia via air cargo.

With directions from an IS commander, Sydney men conceal "a military grade explosive", inside a meat mincer.

Khaled Khayat, 49, allegedly escorts his brother, Amer Khayat, to Sydney Airport on July 15, 2017 to board a flight to Abu Dhabi with luggage containing the bomb.

The bag is not checked in and Amer Khayat, who was no aware of the bomb, boards the plane.

The device is dismantled and plot is abandoned.

Police find parts of the IED during raids in Sydney on July 29 and 30.

Plot B: The toxic gas Following the failed plot on July 15, IS sends further instructions to Sydney terror accused to create a "chemical dispersion device".

Experimentation using precursor chemicals carried out in Sydney to try and make hydrogen sulphide.

IS operative talks of placing device in crowded spaces or public transport however police say device was still a long way from being finished.

International spy agencies tip off Australian authorities about threat to aviation on July 26.

Six properties raided as counter-terrorism operation rolled out in Surry Hills, Lakemba, Punchbowl, Wiley Park and Bankstown, on July 29. Four men arrested.

Police unc precursor chemicals and IED components during raids.

