Airline pilots are challenging a push to bring in compulsory testing for drug and alcohol use.
The government announced yesterday that testing would become mandatory in commercial aviation and the maritime industry from 2017.
It said it was acting to improve public safety after several reports into a hot air balloon crash in Carterton in 2012.
The crash killed 11 people, and the pilot had traces of cannabis in his system.
The Transport Accident Investigation Commission (TAIC) welcomed the move, saying Carterton was not a one-off.
It said there had been eight substance-related accidents between 2004 and 2014, including Carterton, with 41 people killed as a result.
However, Airline Pilots Association senior technical officer Dave Reynolds said airline pilots should not be tested for drugs or alcohol because they were responsible employees.
"They are professional people with professional standards," he said.
"We have a very good peer support network amongst pilots... In terms of the purely medical, legal side of it, we will have to have a word with our legal colleagues.
"We will not rule anything in and we will not rule anything out. It largely depends on the advide of our legal advisers."
Drug or alcohol testing could be very stressful for pilots and could contribute to them suffering fatigue, Mr Reynolds said.