In the closing days of the Vietnam War in 1975, Operation Babylift saw 3,000 babies and infants bundled onto aircrafts to be urgently flown out of Saigon.

They were taken from orphanages and hospitals and evacuated to nations around the world, including America and Canada.

Almost 300 landed in Australia, where they were subsequently adopted.

Next month, some of those adoptees will return to Vietnam to mark the 40th anniversary of the evacuation.

Many were on a long quest to find their birth parents and some turned to DNA testing for help.

Chantal Doecke was on board a plane that took off on April 5, 1975.

"I got put in a shoebox, like most of the other babies did," Ms Doecke said.

"Obviously it was an easy option and a secure option."

Adopted by an Australian couple, she said she never thought much of her heritage until she had her first child.

"And I'd stand there in front of a mirror and I'd hold her and I'd look at her and I'd look at me and I thought wow, she looks like me.

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"But then I'd go - well, I don't know who I look like.

"So that started to bother me."

Ms Doecke searched unsuccessfully to find her birth parents for many years.

Next month she plans to attend an adoptees reunion dinner in Ho Chi Minh City.

Chantal Doecke was adopted by an Australian couple after the Vietnam War ended. ( Supplied )

"Even today, I mean I'm 40 now and I have always constantly tried to change my appearance," she said.

"Not that I'm embarrassed to be Vietnamese or that I look different, I just think it's the whole identity thing with me."

Perth woman Sue Yen Byland searched for her birth parents for nine years.

She said her mother was Vietnamese while she thought her father was an American veteran.

"I feel like I've done everything within my power to put myself out there and to let the woman who's my mum know that I'm looking for her," Ms Byland said.

She also planned to attend the reunion dinner.

"Any one of us could have been placed in the other person's shoes, to look across and to look at a Swedish-speaking adoptee and go, 'well, that could have been me'."

Father found on Facebook

Neither woman had yet used DNA technology in their search for their families, unlike American woman Tricia Houston.

Tricia Houston says her experience offers hope for others still searching for their birth parents. ( Supplied )

Rather than being of mixed race, as she was always told she was, through DNA testing she established that both her birth parents were Vietnamese.

She first found her father on Facebook, where the Vietnamese man detailed his 38-year search for his daughter.

"This man looked really sad and like he was searching for someone all his life," Ms Houston said.

DNA test results matched the two as father and daughter and Tricia plans to return to Vietnam next month to meet her father for the first time.

"I hope this story serves as hope that there is a possibility to find birth family members," she said.

In the United States, a DNA database has resulted in at least a dozen adoptees finding their birth parents.

Thousands more had found extended relatives like cousins, but there was no such database in Australia.