Five terror suspects, including Abu Hamza al-Masri, were flown out of Britain on a jet bound for the United States on Friday.
Officers from Scotland Yard delivered the men to US Marshals at RAF Mildenhall in Suffolk.
A police convoy took the suspects from Long Lartin prison in Worcestershire to Suffolk at 7.15pm.
High Court judges in London earlier dismissed the men's final appeal against extradition to the United States to face terror charges.
Abu Hamza, 54, a one-eyed radical preacher from Egypt, achieved notoriety for praising the September 11 2001 attacks on the United States.
Washington accuses him of supporting al Qaeda, aiding a kidnapping in Yemen and plotting to open a US training camp.
High Court judges in London ruled on Friday that he and Babar Ahmad, Syed Talha Ahsan, Adel Abdul Bary and Khaled al-Fawwaz failed to show "new and compelling" reasons not to send them.
In a statement, Home Secretary Theresa May said she was pleased that the court decision meant "these men, who used every available opportunity to frustrate and delay the extradition process over many years, could finally be removed".
"This government has co-operated fully with the courts and pressed at every stage to ensure this happened,'' she said.
"It is right that these men, who are all accused of very serious offences, will finally face justice."
The BBC reports that once he lands in the United States, Abu Hamza is set to appear in front of a judge within 24 hours in an open hearing.
He is expected to be held at the Metropolitan Correction Centre in New York in an area reserved for high-profile prisoners.
A pre-trial hearing is likely to take place within about three weeks.
The BBC understands a Gulfstream jet owned by the US Department of Justice arrived at the base on Tuesday from Washington.