Be happy whether you get a part credit or a full credit. In New Zealand the airlines are more restrictive. If you get a non-refundable non-changable ticket here (and most of the discounted ones are) then you get NOTHING if you can't use it. Not a dollar. Not a cent back. Just a worthless piece of paper. I'm sure it's something to do with the tiny population here by comparison to the USA - If an airline tried that baloney in the USA they probably wouldn't last too long.