The US military flight to New Zealand - and the secret cargo it carried

The C-17 Globemaster, photograph at Auckland International Airport. Photo / Daniel Talbot

It left as it arrived - with no fanfare and carrying a secret cargo.

For just a shade over 24 hours, Auckland hosted a United States Air Force C-17 Globemaster which came bearing a secret cargo and sealed flight plans.

It came from the East, early on Thursday morning, flying over Great Barrier Island and the Hauraki Gulf before landing at Auckland International Airport.

This morning it took off towards the East - then banked and headed across the Tasman.

For this particular aircraft, it is not unusual to be undertaking vast, globe-trotting flights.

With a 5000km range and a cargo load around 250,000kg, the C-17 is a USAF workhorse for moving freight, soldiers and weaponry around the world.

What it carried to New Zealand, though, is secret.

The United States Embassy would not disclose where it was going or where it had come from, even though the information was able to be harvested from public sources.

In this case, it showed the aircraft at Cape Canaveral a few days ago, then flying to Honolulu before flying to Auckland - with a likely Pacific stop-off en route.

The US Embassy spokeswoman said: "The C-17 is transporting equipment on behalf of the US Government.

"For operational security reasons we do not routinely provide details of cargo being transported on US military aircraft."

The spokeswoman said the US had co-ordinated approvals for the flight with our government.

Security specialist Dr Paul Buchanan, of 36th Parallel Assessments, said: "It sounds like an equipment drop and lift."

He said the landing at Auckland's public international airport was telling and suggested a number of possible reasons.

Among those was speculation the flight was equipment for Rocket Lab, the Kiwi company launching satellites into space from Mahia Peninsula with a manufacturing base in Auckland.

A Rocket Lab launch at Mahia. Photo / Daniel Talbot

Rocket Lab has put more than 30 satellites into orbit, mostly from its launch pad at Mahia Peninsula on the east coast of the lower North Island. It has delivered satellites to orbit for the US Air Force and Nasa.

Buchanan said it was also possible the aircraft was collecting special forces soldiers from the NZ Special Air Service, based just 20 minutes' drive from Auckland airport at Papakura. He said it was possible they could have been collected for transport to Australia for training.

NZDF offered no answers, even refusing to say whether the aircraft would be using Royal NZ Air Force runways or equipment.

New Zealand's relationship with the US has grown closer militarily over the past decade with a focus on our forces operating as part of a coalition of allied countries, led by the US.

The closeness of the relationship has placed New Zealand in a delicate position given its economic reliance on China and increased friction between that country and the US.