Friction among some Air New Zealand pilots over flying by those aged 65-plus has spilled into the open.
Renewed tension over the age of some pilots forced the airline to seek a legal opinion which has resulted in a review of rosters, while the pilots' union says it has been forced into an "invidious position".
More flying of wide-body planes across the Tasman has brought the issue to a head, with a union leader saying most agitation was from a small group of younger pilots worried about career progression.
A 19-page dossier sent anonymously to the Herald details the concerns of some pilots and accuses both the airline and union of not being honest, transparent or open.
A cover letter says the dossier was sent anonymously "as every pilot is **** scared of sharing this information as they are scared of the personal repercussion".
It says some older pilots were very good, "some not so", and there had been an effort to "hide behind the Human Rights Act to accommodate a few at the expense of many - and the public test".
An unsigned letter addressed to the Civil Aviation Authority in March has also been included in the dossier. It acknowledges the legal right of pilots aged over 65 to fly within New Zealand while asking for greater clarity over international operations.
The writer lists a number of safety concerns.
The authority says it won't respond to specifics raised in a letter it doesn't know the origins of, but says it is satisfied that the combination of pilot medical certification, regular pilot competency assessments, on-going monitoring by airlines and regulatory oversight provides a "sound basis for aviation safety".
The CAA, Air NZ and the New Zealand Air Line Pilots Association (ALPA) all point to the human rights and employment law on both sides of the Tasman as guaranteeing the right of pilots over 65 to keep flying here and in Australia and some Pacific Island jurisdictions covered by legislation here.
Human rights law prevents employment discrimination on the grounds of age, which puts New Zealand (and Australia) at odds with global rules covering pilots.
The International Civil Aviation Organisation (ICAO) has a standard which prohibits pilots who reach the age of 65 from operating commercial planes which use more than one pilot.
The New Zealand government, as a member state of ICAO, filed a "difference to the standard", which means pilots over 65 are legally able to fly commercial aircraft within New Zealand and to other territories which also do not apply the standard such as Australia.
Historically, the A320 has predominantly flown domestically and to Australia and pilots over 65 have been able to be "reasonably accommodated". Wide-body aircraft have predominantly flown to destinations that follow the ICAO standard, meaning pilots over 65 have not been able to be reasonably accommodated on those aircraft - Boeing 787s and 777s.
Because these planes were previously flown mainly to areas where the standard applies - United States-controlled airspace specifically - there was not considered to be a viable amount of flying for the over 65s to be reasonably accommodated within rosters.
Legal advice to Air New Zealand says it is required to accommodate pilots over 65 to operate wide-body aircraft in airspace where the ICAO Standard age restrictions have not been adopted, "if we are able to do so without unreasonable disruption to our business".
A spokeswoman says rostering changes are needed to achieve this and the airline was now reviewing them.
President of ALPA, Tim Robinson, says a number of younger pilots were "quite concerned" about older pilots staying on to fly the bigger planes - where they can earn $300,000 or more. That is significantly more than on single-aisle A320s.
"They feel that is going to affect their career progression and slow down promotion opportunities," says Robinson, a 777 pilot. "I would say that's their biggest concern, even though they may not come out and say that."
The union was not trying to reach a majority decision but trying to comply with the law which had been tested and upheld in court cases, notably a Supreme Court ruling (below) in favour of an Air NZ pilot David McAlister in 2009. It was found the airline failed to afford him the same conditions of work as other employees, on account of his age.
"It's not about pleasing as many pilots as possible. If they hold a valid medical a valid medical, are passing simulator checks, passing route checks and qualified pilots then irrespective of the age they should be able to fly the aircraft."
There would be a small number of pilots at Air New Zealand in their late 60s.
"I personally haven't seen significant degradation of pilots once they reach a certain age that would concern me overly."
Robinson says more cognitive testing for pilots who are older is the subject of international discussions.
The CAA says no cognitive ability risk tests were undertaken here.
"However, pilots must undergo simulator training every six months and demonstrate that they continue to meet competency standards," a spokesman says.
Robinson says "angst" among pilots had ebbed recently as they became more familiar with the law.
In a letter to members ALPA says it is in a very "invidious position as we try to represent the needs of ALL our members whilst respecting the democratic nature of the organisation and the need to remain united as a group".
Pilots flying beyond 65 is increasing around the world. Japan has increased the limit to 68 and European Union is discussing pushing up the limit as the pilot shortage intensifies and life expectancy increases and better medicine keeps people in better health into later life.