The tallest fire trucks needed to battle Auckland's SkyCity blaze were out of service or partially broken when the fire started, a union boss says.

New Zealand Professional Firefighters Union vice president Joe Stanley claimed the fire could have been put out within two hours if at least two of the units had been immediately available.

The fire burned for nearly 30 hours, pumping tonnes of potentially toxic smoke into the air, wreaking havoc on the Auckland central business district and further damaging the unfinished $700 million New Zealand International Convention Centre.

Premium - FENZ withdraws Auckland aerial