Police and AFP have focused on a unit in Lakemba. Credit:Michele Mossop Police allege the group of Sydney men were planning to use an "improvised device" to target the aviation industry, however no details on a particular target, location, time or date have been uncovered. Australian Federal Police Commissioner Andrew Colvin said they had no reason to believe airport security had been "compromised" but a heightened state of security has been implemented. Mr Turnbull urged people to limit carry-on and checked-in baggage and to arrive much earlier for domestic and international flights. He said additional measures were put in place at Sydney Airport on Thursday ahead of the operation.

Police raid a home in Lakemba on July 30 over an alleged plot to bring down a plane. Credit:Michele Mossop "These and further measures have been extended to all major airports around the country overnight," he said. "Some of the measures will be obvious to the public, some will not be. Travellers should be prepared for additional scrutiny at screening points." Mr Turnbull has cautioned travellers to arrive early. Credit:Luis Ascui He said domestic travellers should be prepared to arrive at the airport at least two hours before their flights.

"They should limit the amount of carry-on and checked baggage so far as possible, as this will help to ensure that security screening is efficient," he said. A man arrested at a home in Surry Hills remained in hospital with head injuries. Credit:Channel Nine News The national terrorism threat level remains at "probable", unchanged since 2014. "Our number one priority is to keep you safe," Mr Turnbull said. 'Additional burden on screening system'

At Melbourne Airport, Qantas staff told passengers the queue had been long during the Sunday morning rush, but it had cleared by mid-morning. Passengers could be seen having their bags checked by airline staff before heading to security, but there were no reports of major delays at security screening points at either domestic or international departures. There was no visible sign of an increased security presence either. Airport officials declined to reveal what the increased security measures were, beyond urging passengers to arrive two hours before their flights in case of delays. "As the measures place an additional burden on the screening system, it may take a little longer than usual to get through the process," the airport said in a statement.

Passengers seemed to be untroubled by the tightened security. Tameka Bullen, 33, said she was confident police and security staff were on top of things as she arrived to check in for a flight to Adelaide. "I know there is a threat, but I'm not really concerned about it, to be honest," she said. "I travel to Bali a lot and I think they do three bag checks there now. They do what they can do." Monique Vandervleut and Tiffany Siciliano, both 22, were also unconcerned as they headed home from a five-day trip to Melbourne.

"It's a good thing they're doing it, but I'm not concerned," Ms Vandervleut said. Forensic teams collect evidence Police expect to be at a unit in Sproule Street, Lakemba, for several days. On Sunday, forensic teams removed bags of evidence and searched the second-floor home belonging to an older couple and some adult children. One neighbour captured dramatic footage of a man in his 30s with just a towel around his waist being taken away in handcuffs. The neighbour said he'd often seen people in religious gear coming and going from the unit. One night recently he saw five men in robes all arrive at the house.

Another neighbour, who wanted only to be identified as Sami, said several homes in the street were evacuated as officers smashed their way through a glass entrance and donned gas masks and oxygen tanks while they searched the unit. A woman who lives above the family said the older man painted her unit a year ago and was "so nice, completely lovely". At the same briefing as Mr Turnbull, Justice Minister Michael Keenan said the plot was the 13th "significant disruption" in Australia and 70 people have been charged as a result of 31 counter-terrorism operations around the country since 2014. "The primary threat to Australia still remains lone actors," he said. "There is still the ability for people to have sophisticated plots and sophisticated attacks still remain a real threat." Australian Federal Police Commissioner Andrew Colvin said early investigations suggest the plot involved the use of an improvised explosive devise to attack the aviation industry.

"Searches are ongoing. This is the start of a very long and protracted investigation," he said. NSW Police Commissioner Mick Fuller urged Sydney residents to go about their business as normal today but to be prepared for disruptions. "Come into the city, take your trains, go to the shops, you shouldn't be concerned in relation to this," he said. "There is not specific information that means you should sit at home." How the raids unfolded About 1pm on Saturday, the Australian Federal Police conducted a number of terrorist raids across Sydney over a suspected bomb plot to bring down a plane.

The raids took place in Surry Hills, Lakemba, Wiley Park and Punchbowl and were not planned but were a rapid response to information about the plot received by police. The bomb squad attended the scene of the Surry Hills raid on Cleveland Street, which was closed for several hours. The family who lived in the raided house on Cleveland Street have been described as "perfectly nice and normal people" by a neighbour whose property backs onto theirs. "We knew them to say hello to and they seemed nice," the woman in her early 30s, who didn't want to be identified, told AAP. An elderly couple lived in the home, the neighbour said, and they had adult children. The neighbour came home while the raid was under way and said there were "heaps" of police at the scene.

With Steve Lillebuen