Investigators didn't directly blame marijuana for the accident, although Chief Commissioner John Marshall said "the possibility that the pilot's judgment was impaired by the use of cannabis cannot be excluded."
Adventure-tourism plays a significant role in New Zealand's economy. About 2.6 million tourists visit each year, according to government statistics, with about one-third participating in sports such as bungee jumping, skydiving or jet-boating.
But safety problems have increasingly come under the spotlight.
"To people thinking of going to New Zealand on an adrenaline sport, think twice," Chris Coker of Britain told the BBC last year. His son, Bradley Coker, 24, was one of nine people killed in a skydiving plane that crashed in 2010. Investigators found the plane was overloaded.
New Zealand's Ministry of Transport said it's carefully considering the investigators recommendations.