In Lockerbie, the Scottish town the plane was flying over when the explosion happened, bagpipes played and wreaths were laid. Later, a service was also held at London’s Westminster Abbey.
In the United States, hundreds gathered for a memorial service at Virginia’s Arlington National Cemetery, attended by US Attorney General Eric Holder.
Pan Am Flight 103, departing from London was bound for New York. It exploded less than an hour after takeoff on December 21st, 1988. Many of the victims were American college students flying home for Christmas.
A former Libyan intelligence official, Abdel baset al-Megrahi, was convicted of the bombing. He was given a life sentence, but Scottish authorities released him on humanitarian grounds in 2009 after he was diagnosed with prostate cancer. He died in Tripoli last year.
Many questions remain unanswered about the attack. The governments of Britain, the US and Libya issued a joint statement Saturday saying they will cooperate to reveal "the full facts" of the case.