Police disrupted the first alleged plot in Australia to bring down an airplane and arrested four men in raids on Sydney homes, officials said Sunday. Prime Minister Malcolm Turnbull said that security has been increased at Sydney Airport since Thursday because of the plot, AP reports. The increased security measures also were extended to all major international and domestic terminals around Australia overnight. "I can report last night that there has been a major joint counterterrorism operation to disrupt a terrorist plot to bring down an airplane," Turnbull told reporters. "The operation is continuing." Australian Federal Police Commissioner Andrew Colvin said details were scant on the specifics of the attack, the location, and timing.
The plotters were apparently making a peroxide-based explosive device rather than using nitrate-based chemicals that can be detected by airport security swab tests, Barton said. The plan most likely was to take the explosive on board in carry-on luggage unless there was a baggage handler involved who could ensure that a stowed bomb exploded near the fuselage where it would be most damaging. The plot was the 13th significant threat disrupted by police since Australia's terrorist threat level was elevated in 2014, Justice Minister Michael Keenan said. Five plots have been executed. Since Australia's terrorist threat level was raised in 2014, 70 suspects have been charged in 31 police operations, Keenan said.