Took 15 years before someone owned up to the Lockerbie one!
From Wiki -
Claims of responsibility
CIA analysis of various claims of responsibility for the bombing
According to a CIA analysis dated 22 December 1988, several groups were quick to claim responsibility in telephone calls in the United States and Europe:
A male caller claimed that a group called the Guardians of the Islamic Revolution had destroyed the plane in retaliation for Iran Air Flight 655 being shot down by U.S. forces in the Persian Gulf the previous July.
A caller claiming to represent the Islamic Jihad Organization told ABC News in New York that the group had planted the bomb to commemorate Christmas.
Other callers claimed responsibility for the "Ulster Defence League".[42][43]
Another anonymous caller claimed the plane had been downed by Mossad.[42][43]
The list's author noted, "We consider the claims from the Guardians of the Islamic Revolution as the most credible one received so far," but the analysis concluded, "We cannot assign responsibility for this tragedy to any terrorist group at this time. We anticipate that, as often happens, many groups will seek to claim credit."[42][43]