Santa's coming, but he's cutting it a bit fine with a backlog of packages piling up at Courier Post warehouses.

New Zealand Post said thousands of parcels have been in its warehouses for days, because of unprecedented demand leading to processing delays.

It said it's well on track to set a record for the most Christmas deliveries this year.

Business is so brisk an extra charter plane has been brought in to get parcels between the North and South Islands.

But New Zealand Post said it's confident everyone's stockings will be filled in time for Christmas Day.