Relatives yesterday paid tribute to an Australian man who died on a flight from Darwin to Singapore, while on his way to Thailand for a family holiday.

Retiree Graham Francis, 71, was travelling with his wife, Judy, to Phuket, where they were to meet their son Mr Ronald Francis, who was flying there from Japan with his family.

The younger Mr Francis, 45, told The Straits Times his father appeared to have suffered a heart attack in the plane's toilet before it landed here early on Tuesday.

He said the toilet door was taken off to get his father out. A doctor and a nurse, who were fellow passengers, tried to resuscitate him, but to no avail.

"He was a great guy, very kind and very giving," the younger Mr Francis said. "He was a very active man who always liked to move and travel, even in retirement."

He added that his father had had a heart operation about 20 years ago to replace a faulty valve. A doctor had said at a check-up six months ago that everything was fine.

"He was very well thought of by many people and I know he will be missed," he added.

Ms Cheryl King - Mr Francis' former wife and Mr Ronald Francis' mother - was due to fly from Melbourne to join the holiday. She told The Straits Times: "It's the saddest 24 hours for a very long time. Even though he was my ex-husband, he was a very, very nice man and we were all very good friends."

In February, a passenger died on a Singapore Airlines flight from New Delhi to Singapore.

The man, a 34-year-old Indian national, had fainted on the plane.

A month before that, a 58-year-old passenger died on a Tigerair flight from Chiang Mai after collapsing on board. The plane was diverted to Suvarnabhumi Airport in Bangkok for medical help, but the man could not be saved.

SilkAir confirmed yesterday that a passenger had died en route from Darwin on Flight MI804, which landed at Changi Airport at 5.45am on Tuesday.

Mr Francis was cremated in Singapore yesterday. His ashes will be returned to Australia today.