An investigation into what's behind a huge increase in mid-air collisions and near misses by trainee pilots can't say if safety has got worse, because Civil Aviation hasn't been collecting enough information.
The Transport Accident Investigation Commission (TAIC) launched an inquiry prompted by figures that show 16 people died in 10 training flights between 2000 and 2011, compared to four deaths from four flights in the previous decade.
The pilot training industry has increased significantly in the last 10 years with tens of thousands more hours spent in the air.
The commission's chief investigator, Tim Burfoot, told Checkpoint it's impossible to tell if safety at the schools is better or worse because the data simply isn't there.
Mr Burfoot says the lack of information recorded by the Civil Aviation Authority (CAA) is concerning.
"If something changed and a problem started to emerge with the previous gathering of data or lack of, we wouldn't actually know that until we started seeing accidents whereas ideally we would like to see that trend so the regulator can then put measures in place to prevent the accident."
The CAA says it has brought in extra staff to help it gather information to figure out whether pilot training is getting worse.
But director Graeme Harris told Checkpoint it won't have any answers for another few years.
"We've already started to build the human resource so we've got additional safety analysts on board and we're building the new IT systems over the next couple of years and works already underway in that regard."
A public inquiry into the incidents is due to finish in September.
Language concerns - report
A report on a double fatality above Feilding has called for an investigation into English language skills among foreign trainee pilots.
It is concerned poor language skills might mean trainee pilots do not understand messages on their cockpit radio but says there is insufficient data available to settle this, and wants research done.
A collision killed the student and instructor of one plane over Feilding in July 2010. The pilot of the other successfully crash-landed.
One of the pilots was a foreign national. The report does not single him out but says neither he nor the occupants of the other plane heard, or understood, vital radio communication before the crash.
TAIC investigator Ian McClelland says the crash was caused by a one-off failing.
He says both pilots issued radio transmissions about flight plans before the crash and if they had responded to the calls and kept a proper lookout they could have taken avoiding action.
The commission says generally fatality rates in New Zealand are no worse than in Australia and the United States.