Montoya's private army of assassins stands accused of hundreds of murders
Colombia has extradited Diego Montoya, alleged to be one of the country's most powerful drug lords, to the US to face trial for murder and drug trafficking.
The charges relate to Mr Montoya's time as leader of the Norte del Valle cartel which, at its peak, reportedly exported 70% of cocaine sold in the US and EU.
Known as Don Diego, he ran a private army accused of 1,500 murders.
At the time of his 2007 arrest by the Colombian military, he was on the FBI's "10 Most Wanted" list.
Mr Montoya arrived aboard a US military plane in Miami, where he is scheduled to appear in court on Monday to face 12 charges including drug trafficking, obstruction of justice, money-laundering and murder.
He faces at least 20 years in jail if convicted.
Earlier, television footage showed the handcuffed 50-year-old in sunglasses and a jacket under a bulletproof vest, being escorted by heavily-armed Colombian police to a military airbase in Bogota.
There, he was handed over to agents of the US Drug Enforcement Administration, the DEA.
His extradition follows those of several other leading members of the cartel which Colombian authorities say has now been mostly dismantled.
With a $5m (£3.4m) reward advertised for the capture of the billionaire known in Colombia's underworld as the "boss of bosses", Mr Montoya was arrested in his home province of Valle del Cauca.
His capture was seen as a huge coup for the government, ending the reign of one of the legends of the Colombian underworld.
"Colombia is closing a chapter in its fight against drug trafficking," police chief General Oscar Naranjo told AFP news agency after the extradition.
"This extradition is perhaps the most important in years."
Officials say Mr Montoya helped found the Norte del Valle cartel, based near the city of Cali.
The FBI said the cartel received help from left-wing guerrillas and right-wing paramilitary groups.
While his army, the Macho Men, has been largely dismantled, the BBC's Jeremy McDermott in Colombia says Mr Montoya's place and the drug smuggling routes he ran have been taken over by a new boss known by the alias Combatant.
Colombia may be claiming another victory on the war on drugs, our correspondent adds, but the flow of illegal narcotics continues largely unchanged.