British Court of Appeal judges have rejected a last-ditch legal bid to block the first flight due to relocate asylum seekers to Rwanda under a controversial UK government policy.
It comes as UN refugee chief Filippo Grandi slammed the plan as "all wrong... for so many reasons".
A planeload of 31 claimants is due to depart tomorrow as part of an agreement reached with Kigali that London said is aimed at deterring illegal migrants from perilous crossings of the Channel by boat.
The Public and Commercial Services union (PCS), which represents more than 80% of Border Force staff in Britain, and charities Care4Calais and Detention Action challenged a High Court judge's refusal to grant an injunction on Friday.
This meant the first flight from England to the east African country could go ahead tomorrow.
Lawyers for the three groups and one person due to be removed asked for the injunction to prevent the 11 people due on that flight from being taken to Rwanda until the full hearing of whether the policy is lawful next month.
Raza Husain QC argued that the judge who refused to block the flight on Friday, Mr Justice Swift, had wrongly decided the "balance of convenience".
But, following an urgent hearing in London today, three senior judges dismissed the appeal, saying there was no error in the decision of Mr Justice Swift.
Lord Justice Singh, sitting with Lady Justice Simler and Lord Justice Stuart-Smith, said Mr Justice Swift had "conducted the balancing exercise properly" and did not err in principle nor in the approach he took.
He added: "He weighed all the factors and reached a conclusion which he was reasonably entitled to reach on the material before him.
"This court cannot therefore interfere with that conclusion."
The British Home Office has defended the policy and Prime Minister Boris Johnson has said his government had anticipated "a lot of teething problems" with the policy.
But, he said, the move is necessary to stop illegal people-smuggling rackets on either side of the Channel.
A second case is being heard in the High Court later this afternoon after Asylum Aid, a refugee charity, applied for an urgent interim injunction to stop the Government flying migrants to Rwanda.
Filippo Grandi, the United Nations High Commissioner for Refugees, said he also wanted to end dangerous journeys by migrants, but reiterated the UNHCR's position that exporting asylum seekers was not the way to address the issue.
"The UK says... we do this to save people from dangerous journeys. Let me doubt that a little bit," he said.
"Saving people from dangerous journeys is great, is absolutely great. But is that the right way to do it?" he asked. "I don't think so."
Britain with its advanced structures and large resources should not be "exporting its responsibility to another country," Mr Grandi said.
The UN refugee chief also warned that the UK move provided a poor example that other countries might follow, with disastrous effect. "The precedent that this creates is catastrophic."
