Services are to be held in Scotland and the US to remember the victims of the Lockerbie bombing 30 years on.
Wreaths will be laid at a memorial garden in Lockerbie to honour the 270 people killed when Pan Am Flight 103 was blown up on 21 December 1988.
A message from the Queen marking the “solemn anniversary” will also be read out at the memorial.
Eleven people in Lockerbie died along with 259 passengers and crew on board the plane bound for New York.
It was the biggest mass murder on British soil in recent history.
The majority of those on board the plane which fell on the town in south-west Scotland were American.
Services will also be held at Syracuse University, Arlington National Cemetery and FBI headquarters in Washington DC.
The Lockerbie wreath-laying will see victims’ relatives join members of the community who assisted in the aftermath of the atrocity.
The Lord Lieutenant for Dumfriesshire Fiona Armstrong will read out a message from the Queen and pay tribute to the “remarkable community” in the town.
“Please convey my warm thanks to the people of Dumfriesshire for their kind message, sent on the occasion of their Remembrance service to commemorate the 30th anniversary of the Lockerbie bombing, which is being held today,” the Queen said.
“I send my prayers and good wishes to all those who will be marking this solemn anniversary.”
Scottish Secretary David Mundell, who is from the town, will also attend the service at Dryfesdale Cemetery.
Speaking ahead of the service, the MP for Dumfriesshire, Clydesdale and Tweeddale said his thoughts and prayers were with the family and friends of everyone who died on that “terrible night”.
“Lockerbie lost its anonymity that night,” he said.
“We went from a quiet small town to a centre of global attention in a few seconds.
“That was the scale of the challenge local people have faced, aside from the horrors of the air disaster itself.”
He said the people of Lockerbie had retained their “dignity and stoicism” throughout and said “strengthening and deepening” the relationships forged with the US should be a priority.
That sentiment was also underlined by First Minister Nicola Sturgeon speaking at Holyrood on Thursday.
“An almost unimaginable tragedy brought out incredible reserves of solidarity, compassion and love,” she said.
“The bereaved showed immense dignity and resilience.
“People in Lockerbie and the surrounding area opened their hearts to those who had lost loved ones.”
She said the link between Syracuse University, which lost 35 of its students in the bombing, and Lockerbie Academy was an example of remembering the past while building “hope for the future”.
The university will remember its victims at a memorial service with an event also planned at Arlington National Cemetery in Virginia, where a cairn made from Lockerbie stone stands in memory of those who died.
A 30th anniversary service will be held at FBI headquarters in Washington DC.
Back in Scotland, a Walk of Peace has been arranged by the Church of Scotland on Saturday to remember those who died.
People will climb Burnswark Hill near Lockerbie in silence following a special service at Tundergarth Parish Church the previous day.
The only person ever to be convicted of the bombing, Abdelbaset al-Megrahi, died in 2012 after being released from Greenock jail on compassionate grounds.
His family is currently making a third attempt to appeal against his conviction.
The Scottish Criminal Cases Review Commission is considering whether there are grounds to refer his case to the appeal court.