A full review of how a crucial oil pipeline was punctured will be done once fuel is flowing to Auckland Airport, Energy and Resources Minister Judith Collins says.
Thousands of passengers have been affected by a jet fuel shortage over the past week, after the damage to the pipeline was discovered last Thursday.
Up to 80,000 litres was spilled at the site of the rupture, which is thought to have been caused by a digger on a farm at Ruakaka, and the pipe's closure has caused widespread flight delays and cancellations.
The closure has also affected petrol and diesel supplies.
Ms Collins told Morning Report the cause of the puncture was still unknown, but the Ministry for Primary Industries has told her the last time anyone dug for swamp kauri on the farm was in 2011.
"And even then it was long way away from where the pipeline actually was located," she said.
"They've said several hundred metres, up to 800m, and they've got pictures of that. So I think it's very up in the air as to what's happened and how it's happened."
The minister said the focus had been on getting the fuel through, but there would be a full review and investigations into what had happened.
She said a fleet of tankers would today start transporting half a million litres of jet fuel a day from Marsden Point to the airport until the pipeline was fixed.
"That's pretty significant because airlines normally get about a million litres a day so we're doing very well with that."
Flight disruption eases
Just a handful of flight cancellations remain, and airline fuel rations have increased, as Auckland Airport's supply problem eases.
Airlines travelling in and out of the city were limited to 30 percent of normal levels, but since midnight this has increased to 50 percent.
Auckland Airport said seven flights have been cancelled today: six international flights and a Great Barrier Island domestic flight.
Ms Collins told Morning Report Air New Zealand had not made any changes to its normal schedule today.
Check out Auckland Airport's website for up-to-date information about affected flights.
More than a dozen Defence Force drivers were now on the roster to help deliver fuel by road from early today.
Navy tanker HMNZS Endeavour was sent to the Marsden Point refinery near Whangarei yesterday to help ferry diesel supplies south, freeing up dozens of commercial tankers to concentrate on moving aviation fuel.
About 20 other Defence Force staff would be assisting fuel distribution efforts.
Major General Tim Gall, who is leading the operation, told Morning Report their drivers would be split between Auckland and Wellington.
"They're part of that convoy between Marsden Point and Auckland Airport ... But also delivering fuel from Wellington to Palmerston North and Napier and some of the outlying airports in the southern part of the North Island."
Major General Gall said all of the drivers have operated tankers previously, in places such as the Sinai Peninsula in Egypt and Antarctica.
The coastal oil tanker Matuku was due to sail from the refinery today with 1.5 million litres of jet fuel onboard, arriving at Wynyard Wharf in Auckland tomorrow.
Auckland City Council was still deciding whether roads near the wharf would have to be closed for public safety reasons because of the number of trucks arriving to load up with fuel.