Border Security Minister Peter Dutton has pleaded for patience and help, with two-hour check-ins the new normal after authorities foiled a Sydney-based plot to bomb a passenger plane.

Mr Dutton says Australia faces 'imminent' security threats and has urged travelers to accept ramped up security measures at the country's airports, and if possible stay away entirely.

'If you don't need to go inside the airport through the security section, then please don't,' he told the Nine network on Monday.

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Passengers are saying they can feel a police presence at Sydney Airport (pictured Monday)

Security has extensively increased at the airports across Australia (Sydney pictured Monday)

Authorities have warned of two hour delays for passengers boarding domestic flights (pictured Monday)

Passengers are warned to arrive at least three hours early for international flights (pictured)

Huge delays come after a terrorist plot to bomb plane at Sydney airport was foiled at weekend

Travelers are taking to social media about the delays at Sydney Airport this morning

Prime Minister Malcolm Turnbull has been assessing the new arrangements with police, domestic intelligence agency ASIO and the Office of Transport Security on Monday morning.

Domestic passengers are being advised to arrive two hours before their flights, and international passengers three hours before, to allow for the extra security checks in place after the plot was exposed.

'I want to thank the travelling public for their forbearance, having to get to the airport earlier and wait longer to get through security,' Mr Turnbull told ABC radio from Perth on Monday.

'(Security measures) will be required for as long as the threat is assessed as requiring them.'

Mr Dutton said the public needed to be the eyes and ears of Australia's security agencies, telling the Nine network they may provide 'that one part of the jigsaw that helps thwart the next terrorist attack'.

Four Sydney men were arrested over the bomb plot on Saturday, but Mr Dutton won't confirm reports Australia only learned of the plan last week via a tip-off from overseas.

With an investigation underway, the Prime Minister was reluctant to comment on details or speculation, about the plot, including whether it involved a bomb or gassing passengers.

'There will obviously be more to say over coming days,' Mr Turnbull said.

'It will be alleged that this was an Islamist, extremist terrorist motivation.'

Prime Minister Malcolm Turnbull said the delays will occur for as long as they see threats

Passengers are taking to Twitter saying they feel safe despite heightened security (pictured)

Although authorities are warning of lengthy delays, some passengers say lines moved fast

Thousands are left with lengthy delays and people are advised to avoid airport if possible

Arriving atleast two hours before a flight could become the new normal authorities say

Delays are caused by extra security measures taking place including several explosive checks

Mr Dutton also won't confirm reports the men may have planned to get carry-on baggage containing a bomb disguised as a meat grinder onto a plane leaving Sydney.

He said Australians must do their part to help police and security agencies dealing with 'always imminent' security threats to Australia.

'They have obviously interrupted what was planned to be a significant event here,' Mr Dutton said.

Travelers have told media they can really feel the extra police presence at the airports now

Authorities said Australia faces 'imminent' security threat urging travelers to accept delays

Heightened security comes after police foiled plane bomb plot at the weekend (pictured)

Four men were arrested over the bomb plot on Saturday found in Sydney suburbs (pictured)

'I want to put a call out this morning ... just to reinforce those times. Three hours before international flights and two hours before domestic flights.'

He told people to stay away from airports unless they needed to be there, drop loved ones kerbside if they could, and not to pass through security check points unless that was essential.

Airlines are now enforcing the new two and three hour arrival advice for domestic and international travelers and security experts say the arrangements will likely be in place for the foreseeable future.

It is advised people stay away from airports unless a passenger on a flight (pictured Monday)

Airport spokespeople have said the airports are only a little more congested than usual

Heightened security measures are occurring across all airports across Australia (Sydney airport pictured Monday)

Travelers at major airports appear to be heeding the new arrangements, and Mr Dutton thanked them for that.

A Melbourne airport spokesman told AAP the city's airport was a little more congested than usual for a Monday morning, but flights were getting away on time.

'We've been very fortunate in that Victorian travelers have really taken onboard the need to get to the airport a bit earlier, so the new measures are being implemented really successfully,' he said.

Brisbane Airport said there were no significant delays on Monday morning, but said passengers should prepare themselves for a ramped up police presence, and slower security processing, and more trace testing for explosives.

The extensive security measures come as a response to plane bomb plot exposed Saturday

While the delays are lengthy, many passengers aren't complaining and instead praise safety