KEY POINTS:
Two planes narrowly avoided disaster over the South Island, missing each other by as little as 30m, according to a new aviation safety report.
The pilot of one of the aircraft, a ski plane on its way from Westland National Park to Mt Cook, saw the mystery Cessna pass underneath him as they flew over Graham Saddle.
They missed each other by 30m to 60m - little more than half the length of a rugby field.
According to the Civil Aviation Authority, the minimum distance between planes is 1000m.
The near miss has been deemed a "critical" safety incident by the CAA - and was followed two months later by an almost identical incident when another Cessna almost hit a training aircraft near Palmerston North.
The CAA said it had investigated the South Island near miss but could not identify the Cessna. It said neither pilot had been in radio contact.
Neither pilot involved in the North Island incident had been in radio contact either. The Cessna came within 80m of the training plane, which had no adequate lookout person.
"They are concerns," said CAA spokesman Bill Sommer, of the North Island near miss. "But how do you mitigate something like that? Lookout is something you're trained for from the word go when you learn to fly. They're looking at putting in a common frequency, because people use [Palmerston North] as a training area."
The CAA's industry safety update, released last week, also identified four major airspace incidents involving large passenger planes - up from none the year before - and four major security incidents. Two planes, one a passenger jet flying from Wellington to Christchurch, came within 300m of each other above Wellington.
Two passenger planes did not seek clearance from the airport's control tower to land or take off.
An airliner landed at Auckland Airport in bad weather, without clearance. The captain and first officer were too preoccupied with the weather, a technical fault and other planes to contact the tower, said the CAA.
"They realised as soon as they hit the ground, 'We should have been on tower.' So they called the tower to say, 'sorry about that.' It's very unusual, something like that," said Sommer.
No action was taken by the CAA in any of the incidents. Sommer said the authority hadn't seen any concerning trends of concern and focused on education to avoid accidents.
"Education is one of the major tools. Rules do work but education works a hell of a lot better. Right at the bottom of the list of tools would be prosecution," he said.
Sommer said New Zealand had a great safety record and there was no need to change procedures.
"The safest place to fly in the world is Oceania."
Rifle allowed in aeroplane passenger cabin
An airline passenger managed to carry a rifle on board a provincial flight - and was only stopped as he boarded another flight out of Auckland.
He told authorities that he had been allowed to carry it on the earlier flight, between New Plymouth and Auckland, because he had told airline staff the gun was broken.
There are no formal security screening procedures for provincial New Zealand flights.
The incident is recorded as one of four major security incidents in the latest Civil Aviation Authority safety report.
Two of the other cases involved unruly passengers and the third involved a man who was boarding an Auckland-bound flight in Australia with a ceremonial knife strapped to his chest. The passenger with the rifle was only pulled aside after he had landed in Auckland and was boarding another flight to Kerikeri.
CAA spokesman Bill Sommer said the New Plymouth airline officers ignored protocol that says all guns should be in the cargo hold.
"That should never have happened. If he was travelling on a large airliner that would have gone through the screening. It's very unusual. Even though it wasn't working it shouldn't have gone in the cabin; that's the rules."
The man willingly gave up the rifle and it was stowed in the cargo hold for the Kerikeri flight.
