I've had no problem getting credit with United for Air New Zealand flights. However, getting credit for Ansett flights has been a problem--until I discovered Hazel at the United Service Center. She has handled the problem twice for me in the past six months. Save all your tickets, boarding passes, etc., as you'll need to submit copies of them (or keep copies if you submit the originals). My mileage kept getting denied until Hazel got involved and figured out what was going on with the ansett codes.