Passengers have been ordered off planes at Auckland Airport after a security breach.

An airport spokeswoman said a passenger running late for a flight went through an arrivals door, avoiding the usual screening procedure through the security processing area.

The breach means everybody in the domestic terminal who has already been screened and either sitting on a plane or waiting in the departure lounges is being put back through the security process.

Aviation Security has started re-screening passengers but there will be flight delays. Please check with your airline to see whether your flight is affected.

We appreciate your patience.

— Auckland Airport (@AKL_Airport) June 27, 2018

The spokeswoman said three flights are immediately affected but there will be ongoing delays as aviation security has to empty the departure area of the terminal, make sure it's empty, and then let passengers back through.

She did not know how long it would take or how many passengers were affected. However, the airport confirmed about 8am that the re-screening procedure had begun.

Auckland man Carl Jackson was on a plane about to depart for Wellington when the passengers were asked to get off and head back to security.

The delay means he will miss a work meeting in the capital - although he said he will just dial-in instead.

He said no one was panicking but massive queues were waiting to go back through security.

The airport spokeswoman said the first focus was clearing all the departure lounges and planes, then finding the passenger responsible.

The terminal has CCTV throughout, she said.

"This will take some time and on top of that they haven't started re-screening yet. We just ask that people be patient with aviation security as they do their job. It's a security breach, this is just what they do."

The Civil Aviation Authority would decide whether the passenger would be prosecuted.

"It's a huge inconvenience for people who have already been screened and are now delayed," the spokeswoman added.

One frequent traveller said he had never seen anything like it.

"Just hundreds and hundreds queuing. The queue to get through security to Auckland is back to the regional departures. Maybe thousands impacted," he said.

- More to come