The family of April Jones will release balloons later to mark what would have been their missing daughter's sixth birthday.
They are also urging friends and well-wishers around the world to do the same in a symbolic gesture of solidarity.
April was abducted while playing on her bicycle on the Bryn-y-Gog estate in Machynlleth, Mid Wales, on October 1 last year. Her sixth birthday, coming so soon after Easter, is the latest painful landmark underlining the family's loss.
The appeal was made on Facebook by Mel Moon, April's cousin, who lives in Adelaide, Australia.
In a statement she wrote: "On April 4, between 6.30-7pm we would like people to get together and let off balloons for April wherever in the world they may be.
"Coral, Paul and family will be letting balloons off on Bryn-y-Gog green around 6.30-7pm if people wish to join them. They would like if people could tie a note to say where they're from and their names to see how far they may go."
It is now more than six months since April was abducted and killed. Since then a relentlessly methodical examination of thousands of acres of rugged terrain around the town has continued unabated.
What is believed to be the biggest police search ever mounted in the UK looks certain to have an unsuccessful conclusion. Dyfed Powys Police announced last month that the operation will finish at the end of April after seven months of exhaustive searching.
"During April officers will be searching specific areas of land with a view to all search areas identified being completed by the end of April," a spokesman for the force said. "There will of course remain a reactive team of specialist officers available to respond to any new information that is received."
Mark Bridger, 47, of Ceinws, near Machynlleth, was arrested the day after April's abduction. He was later charged with abduction and murder and conspiracy to pervert the course of justice. He is scheduled to stand trial at Mold Crown Court on April 29.