"We're going to be working hard to retain that 777 work in New Zealand so that gives us time to find alternatives and time for the political parties to get the New Zealand dollar down so we can be competitive on the world stage," he said.
When the airline last year announced the revamp of its eight 777-200s, which will involve new seats and entertainment systems, it said the work would be worth $100 million.
Crang said the threat to the heavy maintenance jobs had been "in the wind" for the past three months. Heavy maintenance can include stripping aircraft back to their airframes and taking off engines for servicing and repairs.
The airline is phasing out its older Boeing 767s and remaining 747s and replacing them with newer aircraft which require up to a third less maintenance.
"It's like when you buy a brand new car - you don't have to put it into the garage as much but if you're driving an old Commodore it's in the garage quite often," Crang said.
Hawaiian Airlines was an Air New Zealand heavy maintenance customer but it too was phasing out its 767s.
Crang said finding replacement contracts from other airlines which still used older planes was being hurt by the high New Zealand dollar.
"There have been productivity gains in double figures over the last three years but they've been eroded."
In a brief statement Air New Zealand said the consultation period over the extent of job losses will run until late September.
"The proposed changes reflect a projected drop in future demand for wide body maintenance services both from within Air New Zealand and from external maintenance customers."
A spokeswoman said the airline would retain some heavy maintenance capability at its Auckland engineering base.
Crang said Air New Zealand was always tough to deal with but this is a joint problem.
"This is a highly engaged work force and we're engaging with the company all the time on this issue. This is a sad, sad day for aircraft engineering."
