Madonna has been granted an interim adoption of the Malawian baby she is trying to adopt, the singer has said in a statement from her publicist.
TV footage showed a woman carrying a child through the airport
The decision by a Malawian court gives the singer and her husband, film-maker Guy Ritchie, temporary custody of 3-month-old David Banda for 18 months.
The child was seen being put onto a scheduled flight from South Africa to London, the Associated Press reported.
A group of Malawian charities has tried to stop the adoption.
They say it is unlawful because Madonna has not lived in the country.
The baby was flown out of Malawi by private jet earlier on Monday.
The singer returned to the UK three days earlier, but David Banda was unable to travel as he did not have a passport.
The couple's statement, issued on Monday evening, said the boy had been given a passport and visa.
"It is expected that the family will be reunited within the next few days," it said.
AP television footage showed a woman carrying the baby through Johannesburg international airport, while three bodyguards tried to prevent reporters from photographing him.
Madonna's publicist Liz Rosenberg told the news agency the star was "going to do her best to not make it a public circus".
During 18 months of temporary custody the couple "will be evaluated by the courts of Malawi per the tribal customs of the country," the statement said.
The Human Rights Consultative Committee of 67 Malawian organisations had been due to go to court on Monday seeking an injunction to halt the adoption process.
But it deferred the move, saying it wanted to interview an unidentified uncle of David's who was "said to be opposed to the adoption plan".
Justin Dzodzi, who chairs the rights group, said it had sent investigators to the orphanage where David lived to "get a feel of what the villagers and relatives feel about the adoption".
He added: "Part of our legal action is dependent on getting some disgruntled people to swear affidavits."
The committee insists that Malawian law prohibits international adoption and requires a minimum of 18 months' assessment.
But Penston Kilembe, director of child welfare in the ministry of gender, Child Welfare and Community Services, said Madonna and her husband had broken no laws.
"The process did not start today - Madonna's people have been pushing the papers for some time and her coming was just to sign the papers to conclude the process," he said.
The child lived at the Home of Hope Orphan Care Centre in a village close to the border with Zambia, after his mother died a month after his birth from related complications.
The boy's father, Yohame Banda, has agreed to the adoption.
"What I want is a good life for my child," he said.