Explainer: what you need to know about the upcoming changes to your flights.

With AAP.

On Saturday, members of the NSW Joint Counter Terrorism Team stormed five homes across Sydney, arresting four men allegedly involved in a credible and “elaborate” plot to bring down an Australian commercial plane mid-flight.

With investigations underway, security was ramped up at all major domestic and international airports around the country over the weekend, with additional screening measures put in place and an increased police presence.

All airlines are cooperating, and have urged passengers to be patient with what is expected to become the ‘new normal’ for air travel.

“Australia has very strong safeguards in place at its airports; these changes are about making them even stronger,” Qantas said in a statement.

“We appreciate the understanding and patience of passengers as we implement these enhanced security measures.”

So what's happening? And how will it affect your journey? If you're due to travel in the coming weeks, here's what you need to know.

There's no need to be alarmed.

Transport Minister Darren Chester told media that while it's important the public is aware of the increased threat, they should "go about their business with confidence".

“Australia’s law enforcement and security agencies are among the best in the world and doing everything within their powers to keep the community safe," he said. "All Australian airports have been asked to exercise increased vigilance in their security operations, including at security screening points and within the terminal area."

So what's changing?

Minister Chester said that while some of the security measures will occur behind the scenes, others will directly impact the way people travel.

These will be most obvious while passing through security, and will include increased trace explosive screening as will as additional checks on cabin and checked baggage.

Immigration Minister Peter Dutton has also urged people not to pass through airport security unless they are travelling.

Expect to queue.

As Jetstar said in a statement, "Customers can expect an increased level of security scrutiny at the airport so it may take a little longer than usual to get through the process."

On Monday morning, passengers were reporting backlogs of up to 90 minutes before passing through security at Adelaide and Sydney domestic airports.

Should I arrive early for my flight?

Yes! All passengers are being advised by airlines, airports and the federal government to arrive at least:

• Two hours prior to their domestic flight; and
• Three hours prior to their international flight.

Are there any changes to what can/can't be taken on board?

No.

However, Jetstar, Qantas and Virgin Australia are all asking that passengers "limit the amount of carry-on and checked baggage they travel with as this will help to ensure security screening is efficient."

How long will the increased security apply?

Prime Minister Malcolm Turnbull on Sunday said the measures will be in place indefinitely; "for as long as the threat is assessed as requiring them".

However, Minister Dutton indicated that ongoing permanent changes may lie ahead.

"We will take it one day at a time in terms of needing to respond to the threat we know about. But there may be lessons that may be learned here and we can apply those respectively," he said.

Anyone who sees or hears something suspicious should call the National Security Hotline on 1800 123 400.

For up to date travel information contact your airline or visit their website.