He was expected to remain in hospital until further medical tests had been completed, and has requested privacy during this time.
Auckland Council's head of emergency management planning Richard Woods was sitting in front of the Mr Chin and said the incident unfolded shortly after take-off.
"We were about five or 10 minutes into take-off and the fella behind me was just not very well. The airline attendant picked up on that pretty quickly, she tried to get him to respond, but he wasn't responding.
"She very, very efficiently pulled him down onto the floor and got the resuscitation pack out and brought him around with the assistance of the other two crew.
"The crew were exceptional and everyone on the plane was extremely impressed. They pilot came down later and everyone was just saying how exceptional the crew had been.
"Once he'd been shocked, he came back around," Mr Woods said.
"They isolated him on the ground, they had him in the recovery position and the machine keeps going, it monitors the heart just to see if CPR's required."
The plane then turned around and landed and the man was rushed to hospital, he said.
"He wasn't very well, but he was certainly breathing and everything by the time we'd landed."
Mr Woods estimated the captain landed the small twin-engine turboprop aircraft five minutes after the flight crew resuscitated the man.
"The emergency landing was very well done, it was perfect, it was a very quick descent, but obviously they were trying to make it as comfortable [as possible]."
A St John Ambulance spokesman said the passenger suffered a serious medical incident -- believed to be cardiac related -- and was taken to Dunedin Hospital in "a very serious condition".
An Air New Zealand spokeswoman said it was not appropriate for the airline to share details of the incident.
"Flight NZ5032 from Dunedin to Wellington, returned to Dunedin after a passenger became unwell," she said.
The passenger was transported to hospital and the flight arrived in Wellington two hours later than its original scheduled landing time, she said.