Radical Islamic cleric Abu Hamza is set to arrive in the United States on Saturday morning following his extradition from the UK alongside four other suspects.
Planes carrying the four men left a miliary base in Suffolk late on Friday night, according to the Home Secretary Theresa May.
The extradition finally went ahead following a last-ditch challenge on Friday, which were rejected by two High Court judges in London.
Mrs May said: "I am pleased the decision of the court meant that 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 added: "We have worked tirelessly, alongside the US authorities, the police and the prison service, to put plans in place so that tonight these men could be handed over within hours of the court's decision.
"It is right that these men, who are all accused of very serious offences, will finally face justice."
A police convoy carrying the suspects arrived at RAF Mildenhall in a police convoy which arrived at the base at around 10pm.
They were handed over to US officials before they were taken aboard the planes which left British soil just before midnight, Scotland Yard said.
A US District Court hearing has been scheduled for two of the suspects in Connecticut this morning, according to officials.
The two men are reportedly heading to the state where an internet service provider was allegedly used to host extremist websites, aboard one of the planes.
Au Hamza and the other two suspects are on another aircraft bound for New York, according to the BBC.