Newshub can reveal an investigation is underway after a container of petrol and a chainsaw containing fuel were checked in as luggage on an international flight out of Christchurch without being detected.
An airline representative group has called the failure "extremely concerning".
The Civil Aviation Authority (CAA) has confirmed the incident, with the prohibited items only being picked up and seized by security at Sydney International Airport before the items were due to be loaded onto another flight to Manila.
The executive director of the Board of Airline Representatives New Zealand, Cath O'Brien, said it's a significant security oversight.
"We do have multiple layers of checks and it is extremely concerning that those checks were not totally carried out."
A Qantas Boeing 737 took off from Christchurch to Sydney on April 22. A chainsaw containing fuel and what the CAA described as a small metal container of petrol was loaded in as cargo.
The plane took off.
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The CAA told Newshub it's "exploring how it was not identified" during screening.
O'Brien said airlines have their own safety obligations and need to operate with confidence, but they rely on aviation security to ensure screening is done with vigilance.
"It's... surprising to me that that wasn't picked up. I would expect that AVSEC (Aviation Security Service) would pick up those types of dangerous goods and to me a chainsaw and a fuel container are both obvious items."
Aviation expert and Ardmore Flying School chief executive Irene King said such incidents are not common - but it's still worrying.
"In my view, this was an aberration. But it is showing that there are some systemic failures."
AVSEC said it's spoken to Qantas to reassure the company the matter's being dealt with appropriately.
A spokesperson for the CAA and AVSEC told Newshub the mistake was a "human error" and all staff are given "sufficient and intensive training" and "regular competency assessments".
The spokesperson said the staff member linked to the incident has received "additional training and competency tests", and there was an investigation and disciplinary process.
In the 12 months to April 30, AVSEC identified 51 "screening failures" - where dangerous goods were not picked up, it said.
The agency said that's equivalent to 1.9 failures per every 1 million bags screened.
Airline Pilots' Association president Andrew McKeen said the concern in this case is the highly flammable nature of petrol.
"The fumes from petrol could fill the cargo space and then you only need an innocuous source of ignition for there to be potentially serious consequences," he told Newshub.
King said the prohibited items passed through multiple areas where they should have been discovered, including at check in, during interactions with the passenger and during scanning.
"What it's saying to me is that the education systems and the awareness systems are not robust."
But she doesn't think the staff member facing disciplinary action is solely to blame.
"You don't slam dunk the guy at the end of the chain. You work out where all the systemic failures are and you address it."
She said that should start with more visible displays of what constitutes prohibited items.
Chainsaws, for example, can be checked in - but not when they're full of fuel.
