Border agencies' systems matched the name of a Kiwi traveller who flew to Auckland from Sydney to his earlier flight from Perth before he landed in New Zealand.
But by the time his identity and travel were confirmed, he had landed at Auckland airport and eluded authorities.
The man appears to have broken the transtasman bubble rules, as flights from Perth to New Zealand had been put on hold while Western Australia grappled with a breach of its MIQ hotels.
If charged, he could face a $4000 fine or six months in jail.
The Covid risk from the man is considered low, as he is now in MIQ and has told health officials that he wasn't at any of the locations of interest associated with cases in Western Australia.
But his travel has highlighted how easy it is to breach the rules in the transtasman bubble, which had only been running for a week at the time of his flight.
Immigration NZ manager Peter Elms told the Herald that the man had a flight from Perth to Auckland via Sydney, but the latter leg was cancelled because the transtasman bubble with Western Australia had been paused.
He flew to Sydney anyway and, after landing, bought a new flight to Auckland.
Asked how the man was able to leave Perth when the city was in lockdown, Elms said flights from Perth to New South Wales were permitted for people who didn't live in downtown Perth.
There were checks at the airport, Elms said, so it appears that the man either wasn't asked if he had been in Perth before boarding his flight in Sydney, or if he was asked, he lied.
"We do know that the airline has a standard process in place for all passengers. This was a question they would ask before they left Sydney for Auckland," Elms said.
He should have also been asked before leaving Perth if he intended to fly on to New Zealand.
"If you're looking at where he possibly misled people, it was potentially in Perth when he left Perth after having his flight [from Sydney to Auckland] cancelled, and then in Sydney, misleading people as to where he had been."
It seemed the checks could be easily sidestepped.
"For somebody who's intent on getting to their end destination, regardless of the rules, it's a straightforward option they can take if they're willing to lie."
There was no flag raised on the man's arrival card once he landed in New Zealand, because he was only asked for the port where he boarded his aircraft.
Elms confirmed the man wrote "Sydney" on his arrival card. Health officials contacted the man after he had left the airport.
Other than airlines screening processes, Elms said border agencies used an automated system matching names and travel details to find possible breaches of travel rules.
The system found the man's name while his flight to Auckland was still in the air.
But the names then had to go to a team who manually go through them to find any legitimate beaches.
By the time the man's travel from Perth was confirmed, the plane had been on the ground in Auckland for an hour.
"It does take a bit of time to go through the list of passengers that the system generates," Elms said.
Immigration NZ was looking into whether the automated system could match names and travel details after travellers check in but before their flight leaves.
"It's about trying to get those names generated pre-departure, if possible, so we can actually stop people boarding planes."
But even then, the system was susceptible to dishonesty. A person could drive from a state in lockdown to a different state in Australia, and then fly to New Zealand - and the system would be blind to their travel within Australia.
"Quarantine-free travel, certainly when it comes to pauses or suspension, it relies heavily on people's honesty, people's ability to understand and follow the rules in place," Elms said.
Elms didn't know the circumstances around the man's travel back to New Zealand.
If the man had simply waited a day, the lockdown would have been lifted and he would have been able to fly to New Zealand without having to break the rules.