Loved ones of the 270 victims of the Lockerbie bombing will gather for memorial services today to mark the 20th anniversary of the atrocity.
Pan Am Flight 103 from Heathrow to New York exploded in the skies above the Scottish town on this date in 1988.
All 259 people on board were killed and a further 11 died on the ground below.
Services will be held in Lockerbie, at Heathrow and in the US to remember those who lost their lives.
In the Borders town a commemorative wreath will be laid at the Dryfesdale Cemetery garden of remembrance.
Dryfesdale and Tundergarth churches are to hold services to coincide with the moment just after 7pm when the plane came down.
Up to 300 people, including relatives and some former employees of the Pan Am airline are expected to attend a private memorial at Heathrow Airport chapel led by the Rev John Mosey, whose daughter Helga died in the disaster.
New York State's Syracuse University, which lost 35 students in the bombing, will hold a memorial and some 500 people are expected to attend a remembrance services at Arlington National Cemetery outside Washington DC.
Prayers will be said and the names of all the victims read out at the Pan Am 103 cairn at the cemetery.
Scotland's First Minister, Alex Salmond, said: "As we approach the 20th anniversary of that harrowing evening and appalling tragedy, my thoughts, and those of my colleagues in the Scottish Government, are with the people of Lockerbie, and with all those who were affected by the events of December 21 1988 on both sides of the Atlantic.
"I know that through the events being organised in Lockerbie, at Syracuse University, and at other locations in the UK and the US, that fitting tribute will be paid to those who so tragically lost their lives and those, in south of Scotland and beyond, whose lives have been affected by the atrocity.
"The anniversary also presents an opportunity to reflect on what has happened since - on the strength that the community has shown in coping with such adversity, on the lasting links that have been established with those in other nations who were touched by the disaster, and the subsequent development of the town and its prospects for the future.
"I offer my support to all involved in marking the anniversary and, in particular, my condolences to those who will be mourning the loss of a loved one."
Former Libyan intelligence officer Abdelbaset Ali Mohmed Al Megrahi was found guilty of mass murder following a trial at Camp Zeist in the Netherlands in 2001.
Al Megrahi, who was recently diagnosed with terminal prostate cancer, has consistently denied responsibility for the bombing and a second appeal against his conviction will be heard by the courts next year.
Jim Murphy, Secretary of State for Scotland, said his thoughts were with those who lost loved ones in the disaster.
He said: "This was the worst terrorist attack on the United Kingdom, killing 243 passengers and 16 crew on board and 11 local people on the ground in Lockerbie.
"Our eternal sympathy goes out to all those who lost family members and friends and who to this day feel the dreadful effects of that terrible event.
"Lockerbie and Scotland pulled together in the aftermath, grieving, healing and commemorating together as a strong community - all our thoughts are with them again today."