Megrahi, seen in the white, boarded a flight at Glasgow
The Lockerbie bomber has left Scotland on board a plane bound for Libya after being freed from prison on compassionate grounds.
Abdelbaset Ali al-Megrahi, 57, was jailed in 2001 for the atrocity which claimed 270 lives in 1988.
The decision to release Megrahi, who has terminal prostate cancer, was made by the Scottish Government.
The White House said it “deeply regretted” the decision and some of the US victims’ families reacted angrily.
A police convoy left Greenock Prison, where Megrahi was serving his sentence, more than an hour after the announcement of his release was made.
He was taken to Glasgow Airport to board the flight to Tripoli, which took off shortly before 1530 BST.
The government said it had consulted widely before Scottish Justice Secretary Kenny MacAskill made his decision on applications for Megrahi’s compassionate release or his transfer to a Libyan jail.
He told a media conference on Thursday that he had rejected the application for a prisoner transfer.
However, after taking medical advice it was expected that three months was a “reasonable estimate” of the time Megrahi had left to live.
He ruled out the option of the Libyan being allowed to live in Scotland on security grounds.
And he stressed that he accepted the conviction and sentence which had been handed to Megrahi.
However, Mr Macaskill said Scots defined themselves by their humanity.
“Mr al-Megrahi did not show his victims any comfort or compassion. They were not allowed to return to the bosom of their families to see out their lives, let alone their dying days. No compassion was shown by him to them.
“But that alone is not a reason for us to deny compassion to him and his family in his final days.”
Mr MacAskill continued: “Our justice system demands that judgement be imposed, but compassion be available.
“For these reasons and these reasons alone, it is my decision that Mr Mr Abdelbaset Ali Mohmed Al-Megrahi, convicted in 2001 for the Lockerbie bombing, now terminally ill with prostate cancer, be released on compassionate grounds and be allowed to return to Libya to die.”
Mr MacAskill had been under intense pressure from the US government to keep Megrahi behind bars, with US Secretary of State Hillary Clinton saying his release would be “absolutely wrong”.
“Compassion and mercy are about upholding the beliefs the we seek to live by, remaining true to our values as a people – no matter the severity of the provocation or the atrocity perpetrated.
Some 189 Americans were among those who died in the airliner explosion.
However, the Scottish Government insisted the decision had been reached “on the basis of clear evidence and on no other factors”.
Reacting to the decision, White House press secretary Robert Gibbs said in a statement: “The United States deeply regrets the decision by the Scottish Executive to release Abdel Basset Mohamed al-Megrahi.
“As we have expressed repeatedly to officials of the government of the United Kingdom and to Scottish authorities, we continue to believe that Megrahi should serve out his sentence in Scotland.
The families of American victims of the Lockerbie bombing reacted angrily to the news.
Kara Weipz, of Mt Laurel, New Jersey, who lost her 20-year-old brother Richard Monetti, said: “I don’t understand how the Scots can show compassion. It is an utter insult and utterly disgusting.
“It is horrible. I don’t show compassion for someone who showed no remorse.”
New York state resident Paul Halsch, whose 31-year-old wife was killed, said of Mr MacAskill’s decision: “I’m totally against it. He murdered 270 people.
Ross MacDonald, Edinburgh
“This might sound crude or blunt, but I want him returned from Scotland the same way my wife Lorraine was and that would be in a box.”
Megrahi was convicted of murder in January 2001 at a trial held under Scottish law in the Netherlands.
A first appeal against that verdict was rejected the following year.
However, in 2007 the Scottish Criminal Cases Review Commission granted him a second appeal.
It subsequently emerged he was suffering from terminal cancer but a bid to have him granted bail was refused.
His second appeal got under way this year but shortly afterwards applications were made for both his transfer to a Libyan jail and release on compassionate grounds.
Earlier this week the High Court in Edinburgh allowed Megrahi’s application to drop his second appeal.