The head of the Civil Aviation Authority says rules may need to be changed to protect pilots from being prosecuted if they report problems such as near-misses or mechanical problems.
Under the current rules, all aircraft operators must report incidents to the authority.
Andrew Shelley, a consultant with Aviation Safety Management Systems, says that isn't happening because of a fear of prosecution and only 1 in 10 incidents are being reported.
Mr Shelley says New Zealand needs to move to the system in the United States where one organisation is in charge of collecting data and another is in charge of prosecutions.
CAA director Graeme Harris says there is no problem with under-reporting by passenger airlines, but admits there are problems with smaller operators.
Mr Harris says incident reports are crucial to maintaining safety and changes may be needed to the Civil Aviation Act to protect operators from prosecution if they come forward.