(CNN) - A 104-year-old Australian scientist has started his journey to Switzerland where he plans to end his life, saying he "greatly regrets" living to his advanced age.
Botanist and ecologist David Goodall is traveling to the Life Circle clinic in Basel, accompanied by a nurse from pro-euthanasia organization Exit International, the group's founder said.
Speaking on his 104th birthday, Goodall said if he had one birthday wish it would be to die. "No I'm not happy. I want to die... It's not sad particularly, what is sad is if one is prevented (from dying)," he told Australian broadcaster the ABC.
The question of whether people should be able to legally seek help to end their lives is a subject of fierce debate around the world.
Euthanasia is still illegal in Australia, including in Goodall's home state of Western Australia, although the state of Victoria plans to allow assisted dying from mid-2019.
Seven US states have a form of physician-assisted suicide, as do a small number of countries including Japan, Belgium and Switzerland. A Western Australia government inquiry into assisted dying is scheduled to report back in August 2018.
Philip Nitschke, founder of Exit International, said the option of traveling to Switzerland to seek medically assisted suicide was open to anyone, provided they had sound reason and fulfilled certain criteria.
"My belief is that any rational adult should have the ability to access the drugs which would give them a peaceful, reliable death," he said.
Born in London in April 1914, months before the outbreak of World War I, Goodall is a respected professor who has held academic positions in the United Kingdom, the United States and Australia, according to Exit International.
After his retirement in 1979, Goodall edited a 30-volume series entitled Ecosystems of the World, written by more than 500 authors.
Goodall told the ABC ahead of his departure, although he was still technically healthy, his physical condition and quality of life was deteriorating. "I might as well not have (my health) getting worse and worse, making me unhappy as it goes," he said.
Goodall has been a member of Exit International for about 20 years and is an advocate of assisted dying for those who have chosen to end their lives.
"If one chooses to kill oneself then that should be fair enough and I don't think anyone else should interfere," Goodall told the ABC.
Nitschke said Goodall will spend a few days in France before he flies to Switzerland to end his life on May 10.
"David is... certainly relieved, he can see the light at the end of the tunnel now he's got things in place," said Nitschke, who's known Goodall for 20 years.
Goodall traveled to Europe on business class thanks to a donation of $20,000 from well-wishers who responded to a GoFundMe website set up in his name.
Nitschke said Goodall had recently attempted to take his own life but ended up waking up in hospital instead, where the doctors' judged he was a risk to himself. He was only discharged after an independent psychiatric review commissioned by his daughter, Nitschke said. "He will be very relieved when the plane actually takes off."
Michael Gannon, president of the Australian Medical Association, said the organization's position was clear that doctors should have no involvement with euthanasia or assisted suicide. "We watch this case with interest especially with proposed laws in my home state, and his home state, of Western Australia... I think it's very sad to hear that someone feels this way," he said.