People who blame Air NZ for Ansett's demise seem to forget that from 1979 until February 2000, managerial control of Ansett was held by News Corporation. Say what you will about Rupert Murdoch's ability to run a media business, but he sure couldn't run an airline. It had a expensive mix of planes of almost every type and size and capital expenditure to upgrade the fleet was almost non-existent. Some say Air NZ should have known better what they were getting into as they had owned 50% since 1995, but News Corp still had managerial control and as anyone who has only a 50% interest in a business will know, it restricts how much information you get. Ansett was already a steaming heap before Air NZ bought the remaining 50%, some argue that News hid the extent of it from Air NZ so that Murdoch had a sucker to pay them cash to exit the Ansett investment before it fell over.
Air NZ should never have bought into Ansett and let it go under under Murdoch's watch like anything else he touches that isn't a newspaper or TV station (hello, Myspace).