Border Protection minister Peter Dutton won't say if Australian intelligence was tipped off by authorities overseas before they arrested four men in Sydney on Saturday.
The Daily Telegraph reported on Monday they planned to create a home made bomb by placing wood scrapings and explosive material inside a piece of kitchen equipment such as a mincing machine.
Police seized part of a domestic grinder and a box containing a multi-mincer for making sausages from one of the men's homes, the media outlet reported.
The plot may have involved smuggling the device in hand luggage onto a flight from Sydney to the Middle East.
But Mr Dutton told Nine Network he was unable to comment.
"There will be lots of speculation around about what the intent was, but obviously all of us have been working hard over recent days and we rely upon the expertise of the Federal Police and ASIO and other agencies," he said.
"That's the work they are doing at the moment. There is a lot of speculation around and I don't want to add to that."
Mr Dutton, who will oversees agencies including the Australian Federal Police, ASIO and Australian Border Force, when he heads a newly created Home Affairs portfolio next year, also declined to comment on whether local authorities were tipped off about the alleged plane bomb plot by their counterparts overseas.
"I can't comment on that, because there's information that I've received that is not publicly available yet, and I think it is an issue for the police to talk about," he said.
Mr Dutton apologised to travellers experiencing delays at Australian airports after security measures were stepped up in response to the latest arrests.
Meanwhile, on Sunday, a magistrate granted police an additional period of detention, which can last up to seven days, to hold the four men while their investigation continues.
The group, which is believed to include two sets of father and son, were arrested when police swooped on five properties in the Sydney suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl on Saturday afternoon.
The plan involved an improvised device and was "Islamist-inspired", police said.
Airport security measures increased
Prime Minister Malcolm Turnbull said airport security measures have been increased and reassured the public of their safety.
"The tight cooperation and collaboration between our intelligence and security agencies is the key to keeping Australians safe from terrorism," he said.
A number of "items of interest" were seized and searches at four of the properties continued on Sunday, with AFP Commissioner Andrew Colvin suggesting they may take "many more days".
"We've taken this threat very seriously," Mr Colvin said.
"You should infer that we think this was credible and there was an intention, and there was quite possibly a capability as well."
Mr Colvin expressed confidence Australia's airport security protocols would have prevented the plans coming to fruition.
Despite this, travellers were warned to expect delays and increased scrutiny at all Australian departure points after security measures were "intensified".
"Some of that will be visible, some of it will not be visible, but it will take more time," Mr Turnbull said.
The plot was the 13th significant conspiracy to be foiled by Australian authorities since the country's terror threat level was raised to "probable" in 2014.
Dr John Coyne, who heads the Australian Strategic Policy Institute's Border Security Program, called it the most "troubling".
"It involves a much more coordinated group, on face value," he told AAP.
"They had that level of planning and they obviously had some expectation of achieving success, which indicates they'd identified a vulnerability themselves."
Mr Colvin said he had no reason to believe the integrity of airport security had been compromised.
Dr Coyne agreed current provisions would have thwarted the plot had it gained momentum. He said since the September 11 attacks in 2001, terror incidents had shifted to regionally-focused incidents - such as the Bali bombings - and then to a domestic lone-wolf trend.
"One data point doesn't make a pattern, but we're seeing a new chapter arising or a return chapter almost," he said.
"This is much more planned and deliberate, if the allegations are correct."
Justice Minister Michael Keenan said 70 people had been charged as a result of 31 terror operations since 2014.
State and federal police agreed Saturday afternoon was the right time to act based on risk assessments, NSW Police Commissioner Mick Fuller said.
"The reality is with terrorism, you can't wait until you put the whole puzzle together," he said.
"You have to go early because if you get it wrong, the consequences are severe."
Opposition Leader Bill Shorten said Australians should feel reassured.
"We do owe a debt of gratitude to our security agencies yet again," he said.
No details have been released about the arrested men, who are yet to be charged.
