The US Justice Department on Monday unveiled new charges against the suspected bombmaker in the 1988 downing of Pan Am Flight 103 after it exploded over the Scottish town of Lockerbie.
The charges come on the 32nd anniversary of the attack that killed 270 people, including 190 Americans.
"I am pleased to announce that the United States has filed criminal charges against the third conspirator, Abu Agila Mohammad Masud Kheir Al Marimi, for his role in the bombing of Pan Am flight 103," US Attorney General William Barr said.
"At long last, this man responsible for killing Americans and many others, will be subject to justice for his crimes," he said.
US prosecutors allege that Mr Masud travelled to Malta from Libya with former Libyan intelligence official Abdelbaset Al Megrahi and Al Amin Khalifa Fhimah.
The Justice Department claims Mr Masud made the bomb, which the three co-conspirators placed in a suitcase on a feeder flight from Malta, ensuring that the luggage would transfer to Pan Am Flight 103, where it was detonated over Lockerbie.
Megrahi was sentenced to life in prison in 2001, but Mr Fhimah was acquitted.
Mr Masud is being charged with “destruction of an aircraft resulting in death” and “destruction of a vehicle by means of an explosive resulting in death".
Mr Barr, who will resign as attorney general later this week, announced charges against both men in 1991 when he served as US deputy attorney general.
He gave Robert Mueller, who headed the Justice Department’s criminal division at the time, the task of investigating the bombing. Mr Mueller went on to lead the special investigation into Russia’s attempts to interfere in the 2016 US election.
"The breakthrough that led to the charges announced today arose when law enforcement learnt in 2016 that the third conspirator had been arrested after the collapse of the Gaddafi regime and had been interviewed by Libyan law enforcement," Mr Barr said.
The attorney general said that Libyan authorities had provided a copy of the interview to US law enforcement.
Prosecutors say Gaddafi had personally thanked Mr Masud for his alleged role in the attack. The criminal complaint also alleges that Mr Masud was involved in the 1986 bombing of the La Belle nightclub in Berlin.
"It is our hope that Libyan authorities will allow Masud to be tried for his crime in the United States," Mr Barr said.
