A bomb scare triggered by a note found on a Qantas plane has caused an evacuation of Queenstown airport in New Zealand on Sunday afternoon.

Police swarmed the airport after a cleaner on QF121 found a note about a bomb.

The police bomb squad searched the plane after the note suggested there was an explosive on board, but found no evidence of a bomb.

Baggage and the terminal building were still being searched and authorities were making inquiries with passengers.

A NZ police spokeswoman said a cleaner found the note on the plane after it landed and alerted police.

No passengers were on board at the time the note was found. Queenstown Airport was evacuated and passengers detained.

Air New Zealand cancelled two domestic flights into Queenstown after the scare.

The Qantas plane was scheduled to return to Sydney at 1:25pm AEST but was delayed until after 3pm.

Fraser Mackenzie said he was at the airport to pick up an unaccompanied minor.

"Everyone seems to be pretty relaxed, to be honest. There's been no announcement made to us," he said.

Mr Mackenzie understood those who had not made it through customs had been evacuated to the runway side of the building, including the person he was picking up.

The passenger had flown in from Melbourne and was not on board the Qantas flight being searched.

Other planes were still taking off from the airport, he said.

He had seen three or four fire engines at the scene.

The terminal reopened later on Sunday afternoon with the airport warning passengers of delays.

Stuff.co.nz with Josh Dye