Auckland Airport's domestic terminal was evacuated for an hour and operations temporarily halted on Sunday after a suspicious item was found in a bathroom.
However, passengers were being ushered back into the terminal at 10.50am, after a specialist explosive-detection unit cleared the scene.
Police say the domestic terminal was evacuated as a precaution and the area cordoned off.
"The domestic terminal was evacuated at 9.40am today, while police investigated reports of a suspicious package," an airport spokesman said.
"Passengers are now being readmitted to the terminal. Auckland Airport thanks passengers for their patience."
Passenger Richard England spoke to NZME about an hour after the fire alarm sounded, shortly before the public was given the all clear.
"Half the passengers are actually still on board our aircraft, which is just sitting on the gate, as are a number of other aircraft," he said.
"There are about 300 odd passengers, I imagine, just milling around out on the apron, although contained by security."
England said the passengers had handled the disturbance well.
"Maybe the little kiddies will start getting a little bit fractious after a while, but at the moment, I suspect it's a big adventure."
Racheal Lyons was talking to the Herald when she saw Jetstar staff walk back inside, while a large crowd of "hundreds and hundreds" were slowly walking back in behind them.
Earlier passengers and staff had been evacuated to the adjacent car park, before being moved further back another block, she said.
Lyons and her family, of Auckland, had just arrived at Auckland Airport and were walking into the Jetstar terminal when they were told there was an evacuation happening.
"It was pretty slow. Initially we were just moved into the car park which I assume they use for the fire drills and then they've moved us back another block behind a car parking building."
She said they weren't told anything and everyone had been just mingling patiently outside.
About 10.50am, she then noticed the Jetstar crew walk back into the building.
"It looks like we're re-opening ... there has been no official announcement people are just following the crowd."