"Engineers checked the aircraft on arrival and immediately confirmed there was no fire.
"What occurred was engine surging which resulted in the sort of backfiring from the exhaust that you might experience in a car."
The names of the flight crew and cabin crew who successfully made the emergency landing would not be revealed, she said.
"However, we can confirm they followed the standard operating procedure for an incident of this nature, including putting the aircraft in a holding pattern while they worked through the standard check list and prepared to land back at Napier airport.
"The aircraft is designed to be able to operate safely on one engine and pilots regularly train for this scenario. The pilots also made two announcements to passengers to brief them on the situation prior to executing a normal landing."
Union E tū said it would ensure all its members involved in the scare had the appropriate after care.
"This will have been a scary experience for the crew and passengers on board," the union's head of aviation Anita Rosentreter said.
"We will be ensuring that our members affected by this emergency have all the support needed to deal with the aftermath."
There would be many questions about how the incident occurred and that the union will be closely involved in the process from here.
"We don't have any further details at this early stage, but we will be representing our members every step of the way.
"Union participation is a vital part of getting health and safety right in any workplace. We are pleased that our relationship with the company means we can work constructively together to minimise risks and respond appropriately when things go wrong.
"This emergency has not become an aviation disaster. I think that's a huge testament to the crew on board.
"One passenger has already been reported in the media saying the flight attendants were 'brilliant, calm, and reassuring'. I think that's the mark of an excellent workforce."
