The Air Force says the fault that grounded a Boeing 757-200 delaying the Prime Minister's delegation to India was a faulty micro-switch.

It indicated that the fault had nothing to do with wear and tear or the age of the aircraft - 23 years old.

"This fault to the warning system was not a regular occurrence and is unrelated to the amount of flying the aircraft has completed," the Air Force statement said.

The faulty switch led to the illumination of a cockpit warning related to the aircraft's spoilers (speed brakes), causing the crew to believe the aircraft was potentially not in take-off configuration.


The system was reset in accordance with Boeing procedures but the fault occurred again during a second attempt at take-off.

John Key said the planes have been reliable since he started using them in 2008.

This was the sixth time has used an Air Force Boeing this year. He used the 757s four times in 2014, and five times in 2015.

The 80 on board the plane were forced to spend a night a Townsville, Australia, and the Mumbai leg of the trip was cancelled.

The Air Force's second Boeing 757-200 was sent to Townsville to pick them up and they arrived in New Delhi early this morning.

The Air Force said technicians were working to make the original aircraft serviceable.

In total the two Boeings fly between 1000 and 1400 hours a year, the Air Force said.

Last financial year that amounted to 469 flights and more than 900,000km - the equivalent of more than 22 times around the Earth.

RNZAF's No 40 Squadron operates two Boeing 757-200 aircraft.


Their duties include transporting personnel and equipment, VIP transport, support to New Zealand Defence Force exercise, aeromedical evacuation and rapid response to humanitarian assistance and disaster relief operations.

The Future Air Mobility Capability project is considering options for replacing the current tactical and strategic airlift fleets (the two Boeing 757s and five C-130 Hercules), which are due for replacement in the early to mid 2020s.

Key said on the trip that there were no plans to bring forward the purchase.