A report into a fatal plane crash in Northland reveals the pilot most likely lost control of the aircraft when a weak fin failed in mid-flight.
The top-dresser went down in Pukenui Forest near Whangarei in November 2005, killing Peter Beatty and Greg Nash.
The Civil Aviation Authority has also established that the plane's emergency beacon was switched off.
This delayed the search by about 12 hours, although investigators do not believe the pilot and passenger would have survived the crash.
Since the accident, new CAA rules have required all planes to install different beacons which are harder to switch off.