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