Australia’s oldest scientist is flying from Perth to Europe to end his life through voluntary euthanasia.

David Goodall, who doesn’t have a terminal illness but whose quality of life has deteriorated at age 104, plans to visit family in France before dying in Switzerland on May 10.

“I no longer find much joy in life. Up to, even up to, say, the age of 90 I was enjoying life. But not now,” Professor Goodall told the ABC.

There were a few tears but most of the friends and family who gathered to farewell Prof Goodall at Perth Airport on Wednesday had prepared themselves to say goodbye.

From his wheelchair, he hugged them all in turn, thanking everyone and wishing them a wonderful life before he and his nurse boarded the plane.

A GoFundMe campaign raised more than $20,000, well exceeding the target, to upgrade them from economy to business class.

Prof Goodall, an Emeritus Professor in ecology at Edith Cowan University, is being assisted by an organisation in Basel and Australian euthanasia campaigner Philip Nitschke.

Dr Nitschke said Prof Goodall attempted suicide about two months ago after suffering a fall, ended up in hospital and his daughter could only get him out after arranging an independent psychiatric review.

The doctors who treated him threatened to prevent him from leaving Australia, arguing he was a danger to himself and not fit to travel, Dr Nitschke told AAP on Tuesday.

On Wednesday, he said Prof Goodall’s daughter Karen had been anxious until he got on the plane.

“It will be a relief when he gets here,” Dr Nitschke said from France.

Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

Suicide Call Back Service 1300 659 467.

-AAP