Massive queues have formed at Auckland Airport after last night's sudden change in alert levels.

Prime Minister Jacinda Ardern announced the alert level changes in a press conference last night.

The changes came into effect at 6am today.

Auckland has moved back to level 3, while the rest of the country moves to level 2, after the new Covid-19 community case.

The new case, a 21-year-old man, tested positive yesterday but left Prime Minister Jacinda Ardern once again frustrated as he went to the gym after getting his test from his GP on Friday afternoon.

There were now possible large-scale risks of transmission because of new locations of interests which forced the Government to raise alert levels.

The man and his family were being moved into Auckland's Jet Park managed isolation hotel.

The Hits Wellington presenter Lauren Mabbett is due to fly out of Auckland back to Wellington at 1pm today.

She didn't get any warning of potential queues and decided to get there early in the hopes of putting her feet up and having a coffee but arrived to find a massive queue of people being ushered through one of the terminal's departure doors.

"They've shut all of the doors except one so the queue snakes right along the front of the taxi stand and goes right back down around the corner.

"There's I don't know how many hundreds of people out there, but I imagine there's going to be a lot of people missing flights."

Mabbett said she had heard a lot of last-minute calls with people's names being mentioned, along with airport staff checking the queue for any affected passengers.

"So far there's been a woman running down the line calling out passengers by name. Some people have been a little bit impatient, trying to cut the queue."

However, when spoken to by the Herald in the half hour she had been in the queue it had been moving quicker than she thought.

"It's pretty much the same length the entire time ... but we're moving.

"I got here at 10, but my flight is at 1pm. I can't imagine the stress that some people are feeling right now if they're running late."

She was confident of getting on her flight, but only because she had allowed several hours of extra time.

"I timed it pretty well."

An Auckland Airport spokeswoman said access to the terminal had been restricted to allow Auckland Airport to manage physical distancing in the terminal.

"However, anyone who can't catch a flight without assistance can take one support person in with them.

"This has been the business response since the first time New Zealand went into higher alert levels."

The airport had advice for those travelling:

• Give yourself more time to check in.
• Only passengers can come into the terminal. Be prepared to have your travel itinerary checked at the door, and you may be asked about your reason for travel.
• If you're unable to catch your flight without assistance, one support person will be able to enter the terminal building with you.
• There might be extra waiting time inside the terminal to ensure everyone can keep a safe space between them and fellow passengers. This might mean additional time waiting to be processed. Please be patient.
• Stay safe and leave space - remember to physically distance.
• Scan with your Covid-19 tracer app and ensure Bluetooth is on or keep a notebook record of your visit to the terminal.
• Wear a mask on your flight and public transport to and from the airport. The airport is also asking people to wear masks inside the terminal.
• Please use hand sanitiser stations around the terminal.

Air NZ has also been contacted for comment.