Auckland Airport's domestic terminal is now open for arrivals and departures, but international flights will not be able to land until Sunday.

The domestic terminal re-opened at 12pm.

But the international terminal will not reopen for departing flights until 5pm - apart from the three aircraft already at the gates - and there will be no arriving flights until Sunday 4.30am.

Two international aircraft remain with their passengers in the gate lounge or onboard waiting to depart.

More than 2000 people stayed overnight at Auckland Airport terminals after the flooding left them cut off.

Most of the international travellers who had to stay overnight in airside areas have moved back through border processing into the public areas of the terminal, the airport said in a statement.

"It's been a really long and challenging night. To travellers who were stranded inside the airport as the floods hit fast - we acknowledge the frustration and thank you for your co-operation with our staff as they worked to keep you safe as a first priority," Auckland Airport chief executive Carrie Hurihanganui.

"Any passengers who need or want to remain inside the terminal until they have made accommodation or travel arrangements are certainly welcome to do so."

Bus transport to the park and ride as well as taxis and ride-share options were available from outside the international terminal for passengers wanting to go to their accommodation or home.

The airport encouraged travellers to get in touch with their airline or check their airline travel app for the latest information about their flights.

A team was assessing and rectifying damage inside the terminals and ensuring systems were safe and able to support normal operations, the airport said.