The cases were challenges brought by the Aviation and Marine Engineers Association and the Engineering, Printing and Manufacturing Union to a determination made by the Employment Relations Authority last November, which found in Air NZ's favour.
Repeated and substantial under-estimates of the hearing time required meant the case was unable to conclude in the four days originally set down, Judge Colgan said.
"Even a doubling of that hearing time in the following week did not conclude the case."
In the early 1990s, Air NZ restructured its aircraft engineering operations into different specialised workforces, each of which focused on particular aspects of engineering work on aircraft, the judgement read.
"As a result of recent and prospective aircraft fleet configurations, Air New Zealand now wishes to have again a generic aircraft engineering workforce in which employees can be allocated to work across a greater range of aircraft which now require less maintenance than their predecessors and to have an engineering workforce which can undertake all forms of aircraft maintenance.
"These range from minor inspections of and repairs to aircraft at terminals between flights (generally known as 'line maintenance') to what has traditionally been known as 'heavy' maintenance in which individual aircraft are taken out of service for long periods for substantial scheduled engineering refurbishment."
Until now, aircraft engineers covered by a collective agreement known as 'the Purple Book' have performed exclusively line maintenance of aircraft.
However, last August Air NZ presented its employees with a proposal to disestablish the specialist line maintenance positions in favour of a single generalised aircraft engineering workforce.
The company's proposal is that about 219 specialist line maintenance positions will be disestablished but about 186 new generalist roles created - covered by separate collective agreements.
The airline expects the new roles will be taken up by engineers who are currently line maintenance engineers operating under the Purple Book.
Evidence showed Air NZ had sound reasons for its wish to restructure its engineering operations, and it had been able to give some assurances that employees' incomes may not be affected adversely - at least in most cases, Judge Colgan said.
But the evidence also indicated there were real issues of rostering and other employment terms and conditions which may have significant repercussions for employees and their families, he said.
The plaintiffs' applications for compliance and injunctive orders have been adjourned sine die [for an indefinite period] to enable the parties to negotiate - if necessary with the assistance of a mediator - variations to the relevant collective agreements.