Lockerbie bombing: Al Jazeera documentary makes Iran link claims
A documentary claims to have uncovered fresh evidence that Iran, not Libya, ordered the bombing of Pan Am flight 103 over Lockerbie in December 1988.
The Al Jazeera programme suggests a Palestinian terrorist group retaliated to an American warship shooting down an Iranian civilian airliner.
The only person convicted of the bombing, Libyan intelligence agent Abdelbaset al-Megrahi, died in 2012.
A total of 270 people died when the plane exploded over southern Scotland.
The Al Jazeera programme quotes a "former senior Iranian intelligence official" Abolghasem Mesbahi as saying "Iran decided to retaliate as soon as possible. The decision was made by the whole system in Iran and confirmed by Ayatollah Khomeini."
Five months before the Lockerbie bombing, Iran Air Flight 655 had been shot down by the USS Vincennes, with the deaths of all 290 people on board.
The US government claimed its navy had mistaken the civilian Airbus A300 for an attacking fighter jet.
Tehran vowed that the skies would rain with blood in revenge.
According to Mr Mesbahi, "the target of the Iranian decision-makers was to copy exactly what's happened to the Iranian Airbus. Everything exactly same, minimum 290 people dead."
Al Jazeera claims to have seen US Defence Intelligence Agency cables which reported that the leader of the Popular Front for the Liberation of Palestine General Command (PFLP-GC), Ahmad Jabril, had been paid to plan the bombing.
It quotes a "classified" cable as saying "money was given to Jabril upfront in Damascus for initial expense. The mission was to blow up a Pan-Am flight."
The investigation, to be broadcast on Tuesday, also quotes a former CIA agent Robert Baer as saying "six days after taking down the Airbus there was a meeting in Beirut, we know where it occurred.
"The Iranians went to the PFLP-GC, the break off faction and said, 'alright, you guys know how to bring down airplanes, bring down five, five civilian airliners'."
Megrahi's family still hope to lodge a fresh appeal against his conviction on 270 counts of murder.
The Libyan lost a previous appeal in 2002, one year after he was found guilty, and dropped a second appeal two days before being released from Greenock jail in August 2009 on compassionate grounds.
Scotland's prosecuting authority, the Crown Office, has previously said the alleged involvement of the PFLP-GC was addressed at the original Lockerbie trial at Camp Zeist in the Netherlands.
In December, the Libyan attorney general announced he had appointed two prosecutors to work on the continuing investigation into the bombing.
For the first time they met Scottish and US investigators who are trying to establish whether there are other individuals in Libya who could be brought to trial for involvement in the attack.