Lockerbie bombing: Britain, United States mark 25th anniversary December 21, 2013 -- Updated 1217 GMT (2017 HKT) Services are being held in the United States and Britain to remember those killed It's 25 years since Pan Am Flight 103 exploded in the skies above Lockerbie, Scotland Syracuse University remembers 35 of its students who were on the plane Prime Minister David Cameron says memories of the 270 dead "have not dimmed" (CNN) -- A quarter of a century ago Saturday, Pan Am Flight 103 exploded in the evening skies above Lockerbie, in Scotland, killing all 259 people on board and 11 more on the ground. Events are taking place in Britain and the United States to mark the 25th anniversary of a bombing that devastated families on both sides of the Atlantic. It remains the deadliest act of terrorism on British soil. Services of remembrance will be held Saturday evening at Westminster Abbey in London and at Dryfesdale Church in Lockerbie. The anniversary will also be marked with services at the Pan Am 103 Memorial Cairn in Arlington National Cemetery and at Syracuse University in New York state, which lost 35 of its students in the disaster. The service, in the university's Hendricks Chapel, will start at 2:03 p.m. ET, the time the bomb exploded (7:03 p.m. in Scotland), and will include the recitation of a specially composed "Common Prayer for Peace." Composed jointly by Hendricks Chapel Dean Tiffany Steinwert and the Rev. Sandy Stoddart of Lockerbie, it includes these lines: "Rising up from the ashes of tragedy, we proclaim our commitment to creating a better, more just world." There will also be remembrance services at the university's Lubin House in New York City. UK Prime Minister David Cameron paid tribute to the "fortitude and resilience" of those affected by the bombing and said it demonstrated how "terrorist acts cannot crush the human spirit." He said, "Though 25 years have passed, memories of the 243 passengers, 16 crew and 11 Lockerbie residents who lost their lives on that terrible night have not dimmed. Over the last quarter of a century much attention has been focused on the perpetrators of the atrocity. Today our thoughts turn to its victims and to those whose lives have been touched and changed by what happened at Lockerbie that night. Cameron said a strong bond between the town of Lockerbie and Syracuse University, which offers scholarships to two Lockerbie students each year, represented a "lasting and optimistic legacy" that had emerged from tragedy. After a three-year investigation, U.S. and British investigators indicted two Libyans for murder in the bombing of the New York-bound Boeing 747. Only one, Abdel Baset Ali Mohmed al Megrahi, was convicted. Megrahi died last year in Libya, having been released from prison in Scotland in 2009 on compassionate grounds because he had terminal cancer. Libya agreed in 2003 to pay $2.7 billion in compensation to the families of the bombing victims, although its late leader Moammar Gadhafi always remained cagey about admitting official Libyan involvement in the bombing.