Faulty switch on air force Boeing 757 left Prime Minister John Key stranded en route to India

A replacement plane had to be flown from New Zealand after the Boeing 757 failed. Photo / File

A faulty micro-switch on an air force plane was responsible for leaving the Prime Minister and 80 delegates stranded in Australia.

A replacement plane had to be flown from New Zealand to pick them up, causing the delegation to miss appointments in Mumbai, India.

The Royal New Zealand Air Force today said a micro-switch on the Boeing 757 plane had been identified as the source of the issue.

A fault in the switch led to a flashing warning in the plane's cockpit, causing the crew to believe the aircraft was not in take-off mode.

The system was reset, but the same thing happened when they attempted to take off a second time.

The air force said it was not a regular fault and technicians were now in Townsville, working to repair the aircraft.

It said the fault was not at all related to the number of hours the plane spent in the air.

New Zealand First's Ron Mark said the jets flew too few hours in military service, with the 23-year-old Boeing 757's only doing about 571 flight hours each year.

But the Defence Force said the aircraft actually flew between 1000 and 1400 hours every year.