On December 21, 1988, Pan American Flight 103 was destroyed by a bomb. All 243 passengers and 16 crew members plus 11 people in Lockerbie, Scotland were killed. The Guardians of the Islamic Revolution and the Islamic Jihad Organization claimed separately that they had planted the bomb. However, Lockerbie conspiracy theories were rampant. In 2011, Libya formally admitted responsibility for the bombing.
Iran was a prime suspect with the most obvious motive of revenge. Five months prior to Flight 103, a US warship had shot down an Iranian civilian aircraft. The theory was that Iran had paid the Liberation of Palestine General Command to carry out the bombing. However, the group denied being involved.
Abu Nidal, a Palestinian terrorist, claimed that he was behind the bombing. Telling only his aides, he then swore them to secrecy. After his death in 2002, the information was released to a newspaper by one of those aides but the aide was unable to provide any evidence or say who had engaged Nidal to perform the act.
South Africa has also been said to have arranged the attack in order to assassinate a UN Commissioner for Namibia. The basis for the theory is that senior South African officials, including their Foreign Minister, cancelled their reservations because they had been tipped off. Bernt Carlsson, the Namibia UN Commissioner did die on the flight.
The CIA is also suspected. The suspicion is based on two US intelligence officials on the flight, who were returning to the US to raise concerns over a drug smuggling route from Europe to American in return for information on militant groups. The mother of one of the deceased agents stated that in her last conversation with her son, his superiors did not know he was flying back to the US.
Now, in 2011 a former Libyan foreign minister admitted that Libya was indeed involved in the Lockerbie bombing but did not believe it was a strictly Libyan operation. In addition, the Libyan government formally took responsibility for the bombing and has pledged compensation to the families of the 270 victims.