Every living veteran who served in Bomber Command during World War Two is being sought for the unveiling of a new memorial.
The International Bomber Command Centre is being built in Lincolnshire, which became known as Bomber County in the war because it had so many RAF bases.
The centre is due to open in 2016 but a memorial spire has already been erected at the site in Lincoln.
Organisers want to invite every veteran to the unveiling on 2 October.
They already have names of 900 veterans but believe there are more still to be identified.
Nicky Barr from the International Bomber Command Centre says they have made some new contacts.
"A lot of the veterans that we've now been able to invite weren't on any comprehensive database or squadron lists," she said.
"We've picked up thus far about 50 that come under that category. We suspect that there's probably, at an estimate, another 100 out there."
The spire stands higher than the Angel of North and will be surrounded by a "wall of names" recording the 55,573 men who lost their lives serving in Bomber Command.
Other elements of the centre will include an exhibition and education space called the Chadwick Centre, an amphitheatre and acres of landscaped gardens.
Anyone knowing of any Bomber Command veteran is urged to register their names by emailing email@example.com or writing to The IBCC, 13 Cherry Holt Road, Bourne, Lincolnshire, PE10 9LA.